Albert Barnes Commentary Psalms 59:7

"Behold, they belch out with their mouth; Swords are in their lips: For who, [say they], doth hear?" — Psalms 59:7 (ASV)

Behold, they belch out with their mouth – The word rendered “belch out” properly means to boil forth, to gush out, or to flow; and then, to pour forth copiously, or in a running stream, as a fountain does. Hence, the word also means to pour out “words”—words that flow freely, words of folly, abuse, or reproach. (Proverbs 15:2), “the mouth of fools poureth out (Margin, belcheth or babbleth) foolishness.” (Proverbs 15:28), “the mouth of the wicked poureth out evil things;” that is, it “gushes over” with wicked things, as a fountain overflows. In this place, the word means that David’s enemies, who were in pursuit of his life, poured out reproaches and threats like a gushing fountain.

Swords are in their lips – Their words are like sharp swords. See the notes at (Psalms 57:4).

For who, say they, does hear? – That is, no one hears who will be able to punish us. They dread no man, and they have no fear of God. Compare the notes at (Psalms 10:11). The words “say they” are, however, supplied by the translators and are not in the original. The language may also be understood as that of David himself—as if no one heard. That is to say, it is no wonder that they thus pour out words of reproach, for who is there to hear and to punish them? The former interpretation, however, is to be preferred. The language then expresses the feelings of David’s enemies, who indulged freely in language of abuse and reproach as if there were none to hear.