Albert Barnes' Bible Commentary
Psalms 140 - Introduction
This, also, is a psalm of David. The occasion on which it was composed is not indicated in the title, but the contents of the psalm leave no room to doubt that it was written at an early period of his life, in the time when he was subjected to persecution - most probably in the time of Saul. The psalm bears every mark of David’s style and spirit; and there can be no doubt that he was the author of it. For the reasons why it may have had a place “here” in the Book of Psalms, see the Introduction to Psalms 138:1. On the phrase, “To the chief Musician,” see the Introduction to Psalms 4:1.