And again I asked him, saying, “Sir, since you have been so patient in listening to me, will you show me this also?” “Speak,” said he. And I said, “If a wife or husband die, and the widower or widow marry, does he or she commit sin?” “There is no sin in marrying again,” said he; “but if they remain unmarried, they gain greater honour and glory with the Lord; but if they marry, they do not sin. Guard, therefore, your chastity and purity, and you will live to God. What commandments I now give you, and what I am to give, keep from henceforth, yea, from the very day when you were entrusted to me, and I will dwell in your house. And your former sins will be forgiven, if you keep my commandments. And all shall be forgiven who keep these my commandments, and walk in this chastity.”
Of Sadness of Heart, and of Patience.
Source: The Pastor (or "The Shepherd") (New Advent)