Tobias is the 17th book of the Bible and one of the historical books in the Old Testament. In the text, Raphael, after revealing his angelic nature, commanded both father and son to tell all the wonders that God had done to them and write it in a book. It is likely that the parts of the book written in first person singular are an autobiography of Tobias the elder. It was written originally during the Babylonian Exile, in the early portion of the seventh century B.C.; and that all except the last chapter was the work of Tobias the elder and his son.
The story naturally divides itself into two parts: the fidelity of Tobias the elder and of Sara to the Lord; and the fidelity of the Lord to Tobias and to Sara through the ministrations of the angel Raphael. The chief purpose of the book is to show that God is faithful to those that are faithful to Him. Tobias the elder carries out God's will through prayer, almsgiving, and his works of mercy in burying the dead. Tobias (the son) and Sara follow God's word through their chastity and prayers.
(Summary by Sean McKinley)