If thou prepare thine heart. Having indicated God's righteousness by these general remarks (Job 11:7-12), and implied that Job's complaints are vain and futile, Zophar, in conclusion, addresses Job once more directly: "If thou ( אתּה) prepare thine heart," cleanse it, that is, of all defilement, direct it, and set it straight (see Psalms 78:8) before God, then such and such results (set forth in verses 15-19) will follow.
And stretch out thine hands toward him. The outward act of worship must follow the inward movement of the heart, for the turning to God to be complete.