Charles Ellicott Commentary Psalms 109:4

"For my love they are my adversaries: But I [give myself unto] prayer." — Psalms 109:4 (ASV)

For my love ... — that is, in return for my love I give myself unto prayer. For a concise expression of the same kind as “I prayer,” see Psalm 120:7, “I peace.” Of course the psalmist means, that in the face of all the taunts and reproaches of his slanderers, he simply and naturally turns to prayer, and, as the context seems to indicate, prayer for them.