3 “O Lord, My stay, and My refuge, and My deliverer”. O Lord, who hast stayed Me, because I sought refuge with You: and I sought refuge, because You have delivered Me. “My God is My helper; and I will hope in Him.” My God, who hast first afforded me the help of Your call, that I might be able to hope in You. “My defender, and the horn of My salvation, and My redeemer.” My defender, because I have not leant upon Myself, lifting up as it were the horn of pride against You; but have found You a horn indeed, that is, the sure height of salvation: and that I might find it, You redeemed Me.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)