Psalms 109:24

My knees are weak through fasting ,..... Either voluntary or forced, through want of food or refreshment; this was verified in Christ, when he kneeled and prayed, and his sweat was as it were great drops of blood falling to the ground; see Psalm 69:10 .

And my flesh faileth of fatness ; or "for want of oil" F11 משמן δι' ελαιον , Sept. "propter oleum", V. L. "propter defectum olei", Eth. Arab. ; the radical moisture of his flesh being dried up like a potsherd, Psalm 22:15 .