For the sin of their mouth - This verse has puzzled all the commentators. If we take חטאת chattath for sin-offering instead of sin, we shall get a better sense. Some of Nehemiah's enemies made a profession of the Jewish religion. Tobiah and his son were allied by marriage to the Jews; for Eliashib the priest had married his grandson to the daughter of Sanballat; and this produced a connection with Tobiah, the fast friend of Sanballat. Besides this very priest had given Tobiah one of the great chambers in the house of the Lord, where formerly the meat-offerings, the frankincense, the vessels, and the tithe of the corn and wine and oil were kept; Nehemiah 13:4, Nehemiah 13:5, Nehemiah 13:7-9. And there were children of Tobiah (probably the same family) who professed to be of the Levites, Nethinim, or children of Solomon's servants; but as they could not show their father's house and their seed, whether they were of Israel; these, and others which were children of the priests, were put out of the priesthood, and out of the sacred service, as polluted; as having sprung from intermarriages with heathens. See Ezra 2:59-62. Tobiah was expelled from the house of the Lord by Nehemiah, and all his household stuff thrown out of doors: Nehemiah 13:7, Nehemiah 13:8. And this was doubtless one ground of the enmity of Tobiah to Nehemiah; and in this verse of the Psalm he may allude particularly to his occupancy of the chamber of offerings, which offerings, instead of being given to the Levites, were consumed by Tobiah and his household. This may be fairly gathered from Nehemiah 13:6, Nehemiah 13:10, Nehemiah 13:11. Here then we have the sin of their mouth; their eating the offerings that belonged to the Levites; so that the temple service was deserted, the Levites being obliged to go and till the ground in order to obtain the means of life. And if we take חטאת chattath for sin-offering, it may refer to promises of sacrifice and offering which Tobiah and his family made, but never performed. They ate instead of offering them; and here was the sin of their mouth, in connection with the words of their lips, and their cursing and lying which they spake, for which the psalmist calls upon the Lord to consume them, that they may not be, Psalms 59:13.