John Wesley on Deuteronomy 26:14

In my mourning - In sorrow, or grieving that I was to give away so much of my profits to the poor, but I have chearfully eaten and feasted with them, as I was obliged to do. Unclean use - For any common use; for any other use than that which thou hast appointed, which would have been a pollution of them. For the dead - For any funeral pomp or service; for the Jews used to send in provisions to feast with the nearest relations of the party deceased; and in that case both the guests and food were legally polluted, Num 19:11,14, and therefore the use of these tithes in such cases had been a double fault, both the defiling of sacred food, and the employing those provisions upon sorrowful occasions, which by God's express command were to be eaten with rejoicing.