22 Jesus saith unto him, I say not unto thee, Until seven times: but, Until seventy times seven.
[AD 253] Origen of Alexandria on Matthew 18:21-22
Or, In whatever the two testaments are in agreement, for this every prayer is found acceptable to God.

Or, because the number six seems to denote toil and labour, and the number seven repose, He says that forgiveness should be given to all brethren who live in this world, and sin in the things of this world. But if any commit transgressions beyond these things, he shall then have no further forgiveness.

[AD 367] Hilary of Poitiers on Matthew 18:21-22
When Peter asked him whether he should forgive his brother sinning against him up to seven times, the Lord replied, “Not up to seven times but up to seventy times seven times.” In every way he teaches us to be like him in humility and goodness. In weakening and breaking the impulses of our rampant passions he strengthens us by the example of his leniency, by granting us in faith pardon of all our sins. For the vices of our nature did not merit pardon. Therefore all pardon comes from him. In fact, he pardons even those sins that remain in one after confession.The penalty to be paid through Cain was established at sevenfold, but that sin was against a man, against his brother Abel, to the point of murder. But in Lamech the penalty was established at seventy times seven times, and, as we believe, the penalty was established on those responsible for the Lord’s Passion. But the Lord through the confession of believers grants pardon for this crime. By the gift of baptism he grants the grace of salvation to his revilers and persecutors. How much more is it necessary, he shows, that pardon be returned by us without measure or number. And we should not think how many times we forgive, but we should cease to be angry with those who sin against us, as often as the occasion for anger exists. Pardon’s frequency shows us that in our case there is never a time for anger, since God pardons us for all sins in their entirety by his gift rather than by our merit. Nor should we be excused from the requirement of giving pardon that number of times [i.e., seventy times seven], since through the grace of the gospel God has granted us pardon without measure.

[AD 407] John Chrysostom on Matthew 18:21-22
(Hom. lxi.) Peter thought that he had made a large allowance; but what answers Christ the Lover of men? it follows, Jesus saith unto him, I say not unto thee, Until seven times, but, Until seventy times seven.

When He says, Until seventy times seven, He does not limit a definite number within which forgiveness must be kept; but He signifies thereby something endless and ever enduring.

[AD 420] Jerome on Matthew 18:21-22
The Lord had said above, See that ye despise not one of these little ones, and had added, If thy brother sin against thee, &c. making also a promise, If two of you, & c. by which the Apostle Peter was led to ask, Lord, how oft shall my brother sin against me, and I forgive him? And to his question he adds an opinion, Until seven times?

Or understand it of four hundred and ninety times, that He bids us forgive our brother so oft.

[AD 420] Jerome on Matthew 18:21-22
(Verse 21, 22.) Then Peter came to him and said, Lord, how often shall my brother sin against me, and I forgive him? Up to seven times? Jesus said to him, I do not say to you, up to seven times, but up to seventy times seven. The Lord's words weighed heavily on him, and they could not be broken like a triple cord. Earlier, he had said, See that you do not despise one of these little ones; and he had added, If your brother sins against you, go and show him his fault, just between the two of you. If he listens to you, you have won your brother over. And he had promised a reward, saying, If two of you agree on earth about anything they ask for, it will be done for them by my Father in heaven. For where two or three gather in my name, there am I with them. The apostle Peter, provoked, asks how many times he should forgive his brother who sins against him, and when he proposes the question, should it be up to seven times? Jesus responds: Not up to seven times, but up to seventy times seven, that is, four hundred and ninety times, so that he should forgive his brother who sins against him as many times in a day as that brother cannot sin.

[AD 430] Augustine of Hippo on Matthew 18:21-22
(Serm. 83. 3.) I am bold to say, that if he shall sin seventy-eight times, thou shouldest forgive him; yea, and if a hundred; and how oft soever he sin against thee, forgive him. For if Christ found a thousand sins, yet forgave them all, do not you withdraw your forgiveness. For the Apostle says, Forgiving one another, if any man hath a quarrel against any, even as God in Christ forgave you. (Col. 3:13.)

(ubi sup.) Yet not without reason did the Lord say, Seventy times seven; for the Law is set forth in ten precepts; and the Law is signified by the number ten, sin by eleven, because it is passing the denary line. Seven is used to be put for a whole, because time goes round in seven days. Take eleven seven times, and you have seventy. He would therefore have all trespasses forgiven, for this is what He signifies by the number seventy-seven.

[AD 430] Augustine of Hippo on Matthew 18:21-22
What then does “seventy times seven” mean? Listen, my friends, to this great mystery, this wonderful gift. When the Lord was baptized, Luke the holy Evangelist there noted down his ancestry, in what order, series and stems that generation had been reached in which Christ was born. Matthew began from Abraham and came as far as Joseph in descending generations. But Luke began to count by going back up in ascending order. Why does the one reckon in a descending and the other in an ascending order? Because Matthew set forth the generations of Christ by which he came down to us, and so he began to reckon when Christ was born from a descending order. Luke begins to reckon in reverse from when Christ was baptized. In this is the beginning of an ascension, for he begins to reckon in an ascending order. Note that in his account he enumerates seventy-seven generations! With whom did he begin his reckoning? Note carefully! He began to reckon from Christ up to Adam himself, who was the first sinner and who parented us into bondage to sin. Luke reckoned up to Adam, and so there are enumerated in toto seventy-seven generations—from Christ up to Adam and from Adam up to Christ. Note seventy-seven! So then if no generation was omitted, there is no exemption of any trespass that ought not to be forgiven. For therefore did he reckon up his seventy-seven generations, which number the Lord mentioned as to the forgiveness of sins; since he begins to reckon from the baptism, where all sins are remitted.

[AD 856] Rabanus Maurus on Matthew 18:21-22
It is one thing to give pardon to a brother when he seeks it, that he may live with us in social charity, as Joseph to his brethren; and another to a hostile foe, that we may wish him good, and if we can do him good, as David mourning for Saul.

[AD 220] Tertullian on Matthew 18:22
Who, moreover, was able to forgive sins? This is His alone prerogative: for "who remitteth sins but God alone? " and, of course, (who but He can remit) mortal sins, such as have been committed against Himself, and against His temple? For, as far as you are concerned, such as are chargeable with offence against you personally, you are commanded, in the person of Peter, to forgive even seventy times sevenfold. And so, if it were agreed that even the blessed apostles had granted any such indulgence (to any crime) the pardon of which (comes) from God, not from man, it would be competent (for them) to have done so, not in the exercise of discipline, but of power.

[AD 407] John Chrysostom on Matthew 18:22
What then says Christ, the good God, who is loving towards man? I say not unto you, until seven times, but, until seventy times seven, not setting a number here, but what is infinite and perpetual and forever. For even as ten thousand times signifies often, so here too. For by saying, The barren has borne seven, 1 Samuel 2:5 the Scripture means many. So that He has not limited the forgiveness by a number, but has declared that it is to be perpetual and forever.

This at least He indicated by the parable that is put after. For that He might not seem to any to enjoin great things and hard to bear, by saying, Seventy times seven, He added this parable, at once both leading them on to what He had said, and putting down him who was priding himself upon this, and showing the act was not grievous, but rather very easy. Therefore let me add, He brought forward His own love to man, that by the comparison, as He says, you might learn, that though thou forgive seventy times seven, though thou continually pardon your neighbor for absolutely all his sins, as a drop of water to an endless sea, so much, or rather much more, does your love to man come short in comparison of the boundless goodness of God, of which you stand in need, for that you are to be judged, and to give an account.
[AD 1107] Theophylact of Ohrid on Matthew 18:22
. This is what Peter is asking: how many times, if one sins and then comes and begs forgiveness repentantly, should I forgive him? He added "sin against me," for if he sins against God, I, a layman, cannot forgive him, but only the priest who has this authority from God. But if he sins against me, then I will forgive him and he will be forgiven, though I am a layman and not a priest. He said, "until seventy times seven," not to limit forgiveness within a number, for it would be absurd for someone to sit and count the occasions until they numbered 490 (that is, seventy times seven). But what He means here is an infinite number, as if He were saying, "However many times he sins and repents, forgive him." He also tells us that we should be compassionate by means of the following parable.