1 Then Tobit wrote a prayer of rejoicing, and said, Blessed be God that liveth for ever, and blessed be his kingdom. 2 For he doth scourge, and hath mercy: he leadeth down to hell, and bringeth up again: neither is there any that can avoid his hand. 3 Confess him before the Gentiles, ye children of Israel: for he hath scattered us among them. 4 There declare his greatness, and extol him before all the living: for he is our Lord, and he is the God our Father for ever. 5 And he will scourge us for our iniquities, and will have mercy again, and will gather us out of all nations, among whom he hath scattered us. 6 If ye turn to him with your whole heart, and with your whole mind, and deal uprightly before him, then will he turn unto you, and will not hide his face from you. Therefore see what he will do with you, and confess him with your whole mouth, and praise the Lord of might, and extol the everlasting King. In the land of my captivity do I praise him, and declare his might and majesty to a sinful nation. O ye sinners, turn and do justice before him: who can tell if he will accept you, and have mercy on you? 7 I will extol my God, and my soul shall praise the King of heaven, and shall rejoice in his greatness. 8 Let all men speak, and let all praise him for his righteousness. 9 O Jerusalem, the holy city, he will scourge thee for thy children's works, and will have mercy again on the sons of the righteous. 10 Give praise to the Lord, for he is good: and praise the everlasting King, that his tabernacle may be builded in thee again with joy, and let him make joyful there in thee those that are captives, and love in thee for ever those that are miserable. 11 Many nations shall come from far to the name of the Lord God with gifts in their hands, even gifts to the King of heaven; all generations shall praise thee with great joy. 12 Cursed are all they which hate thee, and blessed shall all be which love thee for ever. 13 Rejoice and be glad for the children of the just: for they shall be gathered together, and shall bless the Lord of the just. 14 O blessed are they which love thee, for they shall rejoice in thy peace: blessed are they which have been sorrowful for all thy scourges; for they shall rejoice for thee, when they have seen all thy glory, and shall be glad for ever. 15 Let my soul bless God the great King. 16 For Jerusalem shall be built up with sapphires and emeralds, and precious stone: thy walls and towers and battlements with pure gold. 17 And the streets of Jerusalem shall be paved with beryl and carbuncle and stones of Ophir. 18 And all her streets shall say, Alleluia; and they shall praise him, saying, Blessed be God, which hath extolled it for ever.
[AD 735] Bede on Tobit 13:1-17
Then the elder Tobias, opening his mouth, blessed God. Confessing His severity and mercy, and at the same time admonishing His faithful to always proclaim His benefits, to fear His scourges; imbued with the spirit of prophecy, he chants many praises concerning our heavenly mother, Jerusalem. And the people of the Jews, converted at the end of the world to faith, will have many teachers and prophetic men who will inflame the minds of their neighbors with heavenly desires, while they frequently resound with the perpetual joys of the heavenly fatherland.

[AD 430] Augustine of Hippo on Tobit 13:14
Everything is loved among friends, and it is so loved that the human conscience feels guilty before itself if it does not love one who returns the love and if it does not give love for love, seeking nothing in a bodily way beyond the signs of good will. From this comes that lamentation, if someone dies, the darkness of sorrow and the heart steeped in tears, by sweetness turned to bitterness, and the death of the living arising from the lost life of the dead. Happy is one who loves God and his friend in God and his enemy because of God. He alone loses no dear one, since all people are dear in God who is never lost. And who is this but our God, the God who is the maker of heaven and earth2 and who fills them up because he makes them by filling them? No one loses God unless he leaves God. And, because he leaves God, where can he go or flee4 except from your pleasure into your ire? For where does he not find your law in his punishment? And “your law is the truth” and “you are the truth.”

[AD 604] Gregory the Dialogist on Tobit 13:17
So as to gladden you in the promise of the joy to come, you know the songs of eternal praise that are written in this book, “Blessed are those who dwell in your house, O Lord; forever they will sing your praise!” And how through a certain wise man19 it is said of the heavenly Jerusalem, “All your squares will be paved with precious stones, and in all your streets they will sing alleluia.” This song of the eternal homeland was proclaimed to us by its citizens, who together cried out, “Glory to God in the highest heavens, and peace on earth to people of good will.”

[AD 735] Bede on Tobit 13:17
Thus our custom is to chant “Alleluia” more frequently and happily during these fifty days in memory of this, our most peaceful and blissful action. Alleluia is a Hebrew word, and in Latin it means “praise the Lord!” Accordingly, where we chant in the psalms, “Praise the Lord,” in place of this expression among the Jews “Alleluia” is always chanted. In his book of Revelation, John the Evangelist mentions that he had heard the throngs of heavenly virtues singing it. And when the venerable father Tobit had understood from an angelic vision what the glory of the citizens on high is, and the great brightness of the heavenly Jerusalem, he said the following with mystical voice, “All its streets are paved with precious and shining stones, and throughout all its districts ‘Alleluia’ will be sung.”It is most proper and beautiful that a general custom has prevailed in holy church of all the faithful throughout the world singing this word of praise in the Hebrew language, out of reverence for the primitive practice. This has come about so that, through the harmony of such a devotion, the whole church may be admonished that now it ought to consist in one faith, confession and love of Christ, and in the future it ought to hurry to that land in which there is no discord of minds, no disharmony of speech. For just as once in Jerusalem the heart and soul of the multitude of the believers was one and all things were theirs in common, so in the “vision of supreme peace” the heart and soul of the entire multitude of those who see God will be one, loving and praising him by whose grace they see that they have been saved. There everything will truly be theirs in common, for, as the apostle says, “God will be all in all.”

[AD 9999] Pseudo-Augustine on Tobit 13:17
Will I ever be able to see what is so desirable, what the angels long to gaze on, so I can say, “Look, now I see what I have so longed for, what I wanted I now possess!”? When will I come and appear before the face of the Lord, to contemplate him in the blessedness of his elect, to know the joy of his people and to glory in his inheritance? When will I see that city of which it is said, “Your squares, Jerusalem, will be paved with pure gold, and in you will resound a hymn of exultation, and in all your streets they will say, ‘Alleluia!’ ”? O holy city, O splendid city! I salute you from afar, I invoke you, I seek you. I desire to see you and to rest in you, but the flesh that holds me back does not let me do so. O desirable city! Your walls are a single stone, your guardian will be God, your citizens will always be glad, since they enjoy forever the vision of God. There is no corruption in you, or defect, or old age or anger—but perennial peace, unchanging glory, eternal joy, continual celebration. Truly there is only joy and exultation, the flower and confidence of youth and of complete salvation. In you there is neither yesterday nor past, but all is today, since yesterday is your tomorrow and the past is everlasting and the same. Health is in you, life is in you, to you belongs infinite peace, and for you God is everything. “Of you they say marvelous things, O city of God.” “All make their dwelling in you with joy.” In you there is no fear or sadness. Every desire is turned into joy, since everything that can be desired is within reach, and everything one could want is there in abundance. All your inhabitants will receive a full measure of happiness, so that all might visibly rejoice together, without end. All will rejoice together, because the brothers and sisters will live together15 when all will gather in a single place. Finally, all will be one, as he who was worthy of his prayer being heard deigned to pray for his family, “As you, Father, are in me and I in you, may they also be one in us.”