John Calvin Commentary Psalms 10:7

"His mouth is full of cursing and deceit and oppression: Under his tongue is mischief and iniquity." — Psalms 10:7 (ASV)

His mouth is full of cursing. The scope of these four verses is this: If God intends to help his servants, it is now a proper time for doing so, since the lawlessness of the ungodly has erupted to the greatest possible extent. In the first place, he complains that their tongues are full of perjuries and deceits, and that they carry or hide mischief and wrongs, making it impossible to have any dealings with them in any matter without loss and damage.

The word אלה, alah, which some translate as cursing, does not signify the curses which they throw out against others, but rather those which they call down upon their own heads: for they do not hesitate to utter the most awful curses against themselves, so that by this means they may better succeed in deceiving others.

It is, therefore, not improperly translated by some as perjury, for this word should be joined to the other two, deceit and malice. Thus the wicked are described as cursing or swearing falsely, insofar as it helps advance their purposes of deceiving and doing injury. This leads to mischief and injustice, because it is impossible for the simple, without suffering harm, to escape their snares, which are woven of deceits, perjuries, and malice.