Carl Friedrich Keil and Franz Delitzsch Old Testament Commentary

The Hiph. הרחיב signifies to make broad, and as a transitive denominative applied to the mind and heart: to make a broad space = to expand one's self (cf. as to the idea, Lam 2:13, "great as the sea is thy misfortune"), lxx ἐπληθύνθησαν, perhaps originally it was ἐπλατηύνθησαν. Accordingly הרחיבוּ is admissible so far as language is concerned; but since it gives only a poor antithesis to צרות it is to be suspected. The original text undoubtedly was הרחיב וממצוקותי (הרחיב, as in Psa 77:2, or הרחיב, as e.g., in Kg2 8:6): the straits of my heart do Thou enlarge (cf. Psa 119:32; Co2 6:11) and bring me out of my distresses (Hitzig and others).