2 The same came to Jesus by night, and said unto him, Rabbi, we know that thou art a teacher come from God: for no man can do these miracles that thou doest, except God be with him.
[AD 407] John Chrysostom on John 3:2-3
Nicodemus saith, "Rabbi, we know that Thou art a Teacher come from God, for no man can do the miracles that Thou doest, except God be with him." He thought he had said something great when he had spoken thus of Christ. What then saith Christ? To show that he had not yet set foot even on the threshold of right knowledge, nor stood in the porch, but was yet wandering somewhere without the palace, both he and whoever else should say the like, and that he had not so much as glanced towards true knowledge when he held such an opinion of the Only-Begotten, what saith He?

"Verily, verily, I say unto thee, Except a man be born again, he cannot see the Kingdom of God."

That is, "Unless thou art born again and receivest the right doctrines, thou art wandering somewhere without, and art far from the Kingdom of heaven." But He does not speak so plainly as this. In order to make the saying less hard to bear, He does not plainly direct it at him, but speaks indefinitely, "Except a man be born again": all but saying, "both thou and any other, who may have such opinions concerning Me, art somewhere outside the Kingdom."

[AD 407] John Chrysostom on John 3:1-2
This man appears also in the middle of the Gospel, making defense for Christ; for he saith, "Our law judgeth no man before it hear him"; and the Jews in anger replied to him, "Search and look, for out of Galilee ariseth no prophet." Again after the crucifixion he bestowed great care upon the burial of the Lord's body: "There came also," saith the Evangelist, "Nicodemus, which came to the Lord by night, and brought a mixture of myrrh and aloes, about an hundred pound weight." And even now he was disposed towards Christ, but not as he ought, nor with proper sentiments respecting Him, for he was as yet entangled in Jewish infirmity. Wherefore he came by night, because he feared to do so by day. Yet not for this did the merciful God reject or rebuke him, or deprive him of His instruction, but even with much kindness conversed with him and disclosed to him very exalted doctrines enigmatically indeed, but nevertheless He disclosed them. For far more deserving of pardon was he than those who acted thus through wickedness.

[AD 407] John Chrysostom on John 3:2
Nicodemus yet lingers below, has yet human thoughts concerning Him, and speaks of Him as of a Prophet, imagining nothing great from His miracles. "We know," he says, "that Thou art a Teacher come from God." "Why then comest thou by night and secretly, to Him that speaketh the things of God, to Him who cometh from God? Why conversest thou not with Him openly?" But Jesus said nothing like this to him, nor did He rebuke him; for, saith the Prophet, "A bruised reed shall He not break, and smoking flax shall he not quench; He shall not strive nor cry": and again He saith Himself, "I came not to condemn the world, but to save the world."

"No man can do these miracles, except God be with him." Still here Nicodemus speaks like the heretics, in saying, that He hath a power working within Him, and hath need of the aid of others to do as He did. What then saith Christ? Observe His exceeding condescension. He refrained for a while from saying, "I need not the help of others, but do all things with power, for I am the Very Son of God, and have the same power as My Father," because this would have been too hard for His hearer; for I say now what I am always saying, that what Christ desired was, not so much for a while to reveal His own Dignity, as to persuade men that He did nothing contrary to His Father.

[AD 407] John Chrysostom on John 3:2
(Hom. xxiv. 1) As yet however he was withheld by Jewish infirmity: and therefore he came in the night, being afraid to come in the day. Of such the Evangelist speaks elsewhere, Nevertheless, among the chief rulers also many believed on Him; but because of the Pharisees they did not confess Him, lest they should be put out of the synagogue. (John 12:42)

[AD 430] Augustine of Hippo on John 3:1-2
(Tr. xi) He had said above that, when He was at Jerusalem—many believed in His Name, when they saw the miracles which He did. Of this number was Nicodemus, of whom we are told; There was a man of the Pharisees, Nicodemus, a ruler of the Jews.

(Tr. xi. c. 3, 4) Nicodemus was one of the number who believed, but were not as yet born again. Wherefore he came to Jesus by night. Whereas those who are born of water and the Holy Ghost, are addressed by the Apostle, Ye were sometimes darkness, but now are ye light in the Lord. (Eph. 5:8)

(Tr. xi. c. 3) What the ground of his belief was, is plain from what immediately follows: For no one can do these miracles that Thou doest, except God be with him. Nicodemus then was one of the many who believed in His Name, when they saw the signs that He did.

(Tr. xi. c. 4) Those then are the persons to whom Jesus commits Himself, those born again, who come not in the night to Jesus, as Nicodemus did. Such persons immediately make professsion.

[AD 430] Augustine of Hippo on John 3:1-2
Therefore, since Nicodemus was of that number, he came to the Lord, but came by night; and this perhaps pertains to the matter. Came to the Lord, and came by night; came to the Light, and came in the darkness. But what do they that are born again of water and of the Spirit hear from the apostle? "Ye were once darkness, but now light in the Lord; walk as children of light"; and again, "But we who are of the day, let us be sober." Therefore they who are born again were of the night, and are of the day; were darkness, and are light. Now Jesus trusts Himself to them, and they come to Jesus, not by night, like Nicodemus; not in darkness do they seek the day. For such now also profess: Jesus has come near to them, has made salvation in them; for He said, "Except a man eat my flesh, and drink my blood, he shall not have life in him."

[AD 444] Cyril of Alexandria on John 3:2
More ready is Nicodemus to believe, but overcome by no good fear, and not despising the opinion of men, he refuses boldness, and is divided in opinion into two, and halts in purpose, feeble upon both his knee joints, as it is written, forced by the convictions of his conscience to the duty of believing by reason of the exceedingness of the miracles, but esteeming the loss of rulership over his own nation a thing not to be borne, for he was a ruler of the Jews. Deeming that he can both preserve his repute with them, and be a disciple secretly, he cometh to Jesus, making the darkness of the night an aider of his scheme, and by his secret coming convicted of double mindedness.

[AD 444] Cyril of Alexandria on John 3:2
Nicodemus imagines that he can become pious enough to attain salvation merely by marveling at the wonders Jesus had done.… Calling Jesus a teacher from God and a co-worker with him, he does not yet know that Jesus is by nature God, nor does Nicodemus understand the plan of salvation according to the flesh. Instead, he still approaches Jesus as a mere man and has only a slight conception of who he is.

[AD 735] Bede on John 3:1-2
His rank is given, A ruler of the Jews; and then what he did, This man came to Jesus by night: hoping, that is, by so secret an interview, to learn more of the mysteries of the faith; the late public miracles having given him an elementary knowledge of them.

[AD 735] Bede on John 3:2
This ruler of the Jews came to Jesus by night, hoping, that is, by so secret an interview, to learn more of the mysteries of the faith; the late public miracles having given him a rudimentary knowledge of them.

[AD 853] Haymo of Halberstadt on John 3:2
(Hom. in Oct. Pent.) Or, well may it be said that he came in the night, enveloped, as he was, in the darkness of ignorance, and not yet come to the light, i. e. the belief that our Lord was very God. Night in the language of Holy Writ is put for ignorance. And said unto him, Rabbi, we know that Thou art a teacher come from God. The Hebrew Rabbi, has the meaning of Magister in Latin. He calls him, we see, a Master, but not God: he does not hint at that; he believes Him to be sent from God, but does not see that He is God.

[AD 1107] Theophylact of Ohrid on John 3:2
Still clinging to Jewish weakness, he comes to Jesus "at night" out of fear of the Jews (John 19:38–39); he calls Him Teacher, as a mere man, for such was his understanding of Him, which is why he adds that no one can perform such miracles unless God is with him. Do you see, he comes to Jesus as to a prophet and a man beloved by God.
What then does the Lord do? He does not rebuke him in a stern manner, does not say, why do you come at night to a Teacher sent from God, why do you lack boldness? He says nothing of the sort, but graciously converses with him about divine and lofty subjects. Note also that although Christ performed many miracles, the present Evangelist does not recount a single one of them, either because they have been told by the other Evangelists, or because they are beyond detailed narration.

[AD 1274] Thomas Aquinas on John 3:2
Then he describes him as to the time, saying, he came to Jesus at night. In regard to this, it might be noted that in Scripture the quality of the time is mentioned as to certain persons in order to indicate their knowledge or the condition of their actions. Here an obscure time is mentioned, at night. For the night is obscure and suited to the state of mind of Nicodemus, who did not come to Jesus free of care and anxiety, but in fear; for he was one of those of whom it is said that they "believed in him; but they did not admit it because of the Pharisees, so that they would not be expelled from the synagogue" (below 12:42). For their love was not perfect, so it continues, "For they loved the glory of men more than the glory of God."

Further, night was appropriate to his ignorance and the imperfect understanding he had of Christ: "The night has passed, and day is at hand. So let us cast off the works of darkness" (Rom 13:12); "They have not known or understood; they are walking in darkness" (Ps 81:5).

Then he is described from his statements, when he says that Nicodemus said to Jesus: Rabbi, we know that you are a teacher come from God. Here he affirms Christ's office as teacher when he says, Rabbi, and his power of acting, saying, for no one could perform the signs you perform, unless he had God with him. And in both remarks he says what is true, but he does not affirm enough.

He is right in calling Jesus Rabbi, i.e., Teacher, because, "You call me Teacher and Lord; and you do well, for so I am," as we read below (13:13). For Nicodemus had read what was written in Joel (2:23): "Children of Sion, rejoice, and be joyful in the Lord your God, because he has given you a teacher of justice." But he says too little, because he says that Jesus came as a teacher from God, but is silent on whether he is God. For to come as a teacher from God is common to all good prelates: "I will give you shepherds after my own heart, and they will feed you with knowledge and doctrine," as it says in Jeremiah (3:15). Therefore, this is not unique to Christ even though Christ taught in a manner unlike other men. For some teachers teach only from without, but Christ also instructs within, because "He was the true light, which enlightens every man" (above 1:9); thus he alone gives wisdom: "I will give you an eloquence and a wisdom" (Lk 21:15), and this is something that no mere man can say.

He affirms his power because of the signs he saw. As if to say: I believe that you have come as a teacher from God, for no one could perform the signs you perform. And he is speaking the truth, because the signs which Christ did cannot be worked except by God, and because God was with him: "He who sent me is with me" (below 8:29). But he says too little, because he believed that Christ did not perform these signs through his own power, but as relying on the power of another; as though God were not with him by a unity of essence but merely by an infusion of grace. But this is false, because Christ performed these signs not by an exterior power but by his own; for the power of God and of Christ is one and the same. It is similar to what the woman says to Elijah: "Because of this I know that you are a man of God" (1 Kgs 17:24).