Psalms 139:13

For thou hast possessed my reins
His thoughts and counsels, the reins being the seat of instruction and counsel; hence God is called the trier of the reins, and searcher of the hearts of the children of men; he is the possessor or master of their most secret thoughts, and thoroughly knows them; see ( Psalms 7:9 ) ( 16:7 ) ; they are also the seat of the affections, which are naturally sinful and inordinate, and set upon carnal and earthly things; but the Lord possesses and engrosses the affections of his people in the best sense, ( Psalms 73:25 ) ; moreover the reins are the seat of lust, the bed in which it is conceived and brought forth, and God knows the first motions of it there; and that the imagination of the thought of man's heart is evil continually, ( Genesis 6:5 ) ;

thou hast covered me in my mother's womb;
with the secundine, or afterbirth, in which he carefully wrapped him, a proof of his knowledge of him, and care for him in the womb; or with skin and flesh he covered his bones with as they grew there; see ( Job 10:11 ) ; or the sense is, he protected and defended him in his embryo state, and when ripe for birth took him out from thence, and held him up ever since, ( Psalms 22:9 ) ( 71:6 ) ; he had his eye on him when no other eye could see him, not even his mother that bare him, and before ever he himself saw light. The Targum is,

``thou hast founded me in my mother's womb.''