Albert Barnes Commentary Psalms 119:129

"Thy testimonies are wonderful; Therefore doth my soul keep them." — Psalms 119:129 (ASV)

Thy testimonies are wonderful - This commences a new division of the psalm, indicated by the Hebrew letter Pe (פ p), corresponding to our “p.” The meaning of the expression here is, that the laws of God—the revelations of his will—are adapted to fill the mind with wonder. The mind is awed by their wisdom; their comprehensiveness; their extent; their spirituality; their benevolence: by the fact that laws are framed, so perfectly adapted to the end; so well suited to secure order, and to promote happiness.

Therefore doth my soul keep them - Because they are so surpassingly wise and benevolent; because they are so manifestly the work of wisdom and goodness.