The opening verses of this book ascribe it, or at least its first part, to Baruch, the well-known secretary of the prophet Jeremiah. It contains five very different compositions, the first and the last in prose, the others in poetic form. The prose sections were certainly composed in Hebrew, though the earliest known form of the book is in Greek.
An observance of the feast of Booths with a public prayer of penitence and petition (Baruch 1:15-3:8), such as is supposed by the introduction (Baruch 1:1-14), would not have been possible during the lifetime of Baruch after the fall of Jerusalem; this indeed is suggested in the prayer itself (Baruch 2:26). The prayer is therefore to be understood as the pious reflection of a later Jewish writer upon the circumstances of the exiles in Babylon as he knew them from the Book of Jeremiah. He expresses in their name sentiments called for by the prophet, and ascribes the wording of these sentiments to the person most intimately acquainted with Jeremiah’s teaching, namely, Baruch. The purpose of this literary device is to portray for his own and later generations the spirit of repentance which prompted God to bring the exile to an end.
The lesson thus gained is followed by a hymn in praise of Wisdom (Baruch 3:9-4:4), exalting the law of Moses as the unique gift of God to Israel, the observance of which is the way to life and peace. The ideal city of Jerusalem is then represented (Baruch 4:5-29) as the solicitous mother of all exiles, who is assured in the name of God that all her children will be restored to her (Baruch 4:30-5:9).
The final chapter is really a separate work, with a title of its own (Baruch 6:1). It is patterned after the earlier letter of Jeremiah (Jer 29), in the spirit of the warnings against idolatry contained in Jer 10 and Isa 44. Its earnestness is impressive, but in restating previous inspired teachings at a later day, it does so with no special literary grace.
Thus the principal divisions of the book are seen to be:
Prayer of the Exiles (Baruch 1:1-3:8)
Praise of Wisdom in the Law of Moses (Baruch 3:9-4:4)
Jerusalem Bewails and Consoles Her Captive Children (Baruch 4:5-29)
Jerusalem Consoled: The Captivity about To End (Baruch 4:30-5:9)
The Letter of Jeremiah against Idolatry ((Bar) Let 6:1-7)