Adam Clarke on Psalms 119:17

Deal bountifully - גמל gemol, reward thy servant. Let him have the return of his faith and prayers, that the Divine life may be preserved in his soul! Then he will keep thy word. From גמל gamal, to reward, etc., comes the name of ג gimel, the third letter in the Hebrew alphabet, which is prefixed to every verse in this part, and commences it with its own name. This is a stroke of the psalmist's art and ingenuity.