Albert Barnes Commentary Psalms 139:17

"How precious also are thy thoughts unto me, O God! How great is the sum of them!" — Psalms 139:17 (ASV)

How precious also are your thoughts to me, O God! - On the word “thoughts,” see the notes at (Psalms 139:2). Compare (Psalms 139:23). The remark is made here doubtless in view of the numberless “thoughts” involved in planning and forming a frame so wondrous, and in the care necessary to bring it to perfection, to develop it, to provide for it, and to guard and defend it. How many “thoughts” of a parent are employed on behalf of his children, in providing for them, teaching them, counseling them, and anticipating their needs. How many more thoughts are necessary on the part of God in reference to each one of us: for there are numberless things necessary for us which cannot occupy the mind of a parent, since he cannot accomplish these things for us; they do not lie within his province, or in his power.

How great is the sum of them - literally, “How strong are the heads of them.” That is, their sum total, or the summing of them up, would be a task beyond human power. And who “could” estimate the number of the “thoughts” necessarily bestowed on himself by his Maker in all the care exercised over him; all the arrangements for his development and growth; all that is done to defend him from danger; all that is indispensable in providing for his needs; all that was necessary to secure the salvation of his soul! See the notes at (Psalms 40:5).