Lord, thou hast heard the desire of the humble (comp. Psalms 9:12). It is not the psalmist's prayer alone that he regards as heard and answered. The oppressed have cried to God against their oppressors, and their cry has "come before him, and entered into his ears."
Thou wilt prepare their heart; rather, thou dost establish (or, make firm) their heart. Through their conviction that thou art on their side, and art about to help them. Thou wilt cause thine ear to hear; or, thou causest.