Thou hast also given me the shield of thy salvation: and thy gentleness hath made me great. See Gill on Psalm 18:35.

36 And Thou reachest me the shield of my salvation,
And Thy hearing makes me great.
37 Thou makest my steps broad under me,
And my ankles have not trembled.
The Lord bestows the true strength for victory in His salvation. The shield of salvation is the shield which consists of salvation, of the helping grace of the Lord. ענתך, for which we find in the psalm ענותך, thy humility, i.e., God's condescending grace, does not mean "thy humiliation," but "thy hearkening," i.e., that practical hearkening on the part of God, when called upon for help, which was manifested in the fact that God made his steps broad, i.e., provided the walker with a broad space for free motion, removing obstructions and stumbling-blocks out of the way. God had done this for David, so that his ankles had not trembled, i.e., he had not been wanting in the power to take firm and safe steps. In this strength of his God he could destroy all his foes.