I delight to do your will, O my God: yea, your law is within my heart.
Read Chapter 40
Augustine of Hippo
14. "In the head of the Book it is written of me, that I should fulfil Thy will: O my God, I am willing, and Thy Law is within my heart" (ver. 8). Behold! He turns His regards to His members. Behold! He hath Himself "fulfilled the will" of the Father. But in what "beginning of a Book" is it written of Him? Perhaps in the beginning of this Book of Psalms. For why should we seek far for it, or examine into other books for it? Behold! It is written in the beginning of this Book of Psalms! "His will is in the Law of the Lord;" that is, "`O my God, I am willing,' and `Thy Law is within my heart;'" that is the same as, "And in His Law doth he meditate day and night." ...
Heart. So the Vatican Septuagint reads; while other editions have koilias, "belly. "(St. Jerome, ad Sum.)
Hebrew, "bowels. "(Haydock)
The sense is the same. (Berthier)
I love the law so much, that I would hide it in my bowels, (Calmet) or in the most secret place. (Theodoret)