Isaiah 55:3

Incline your ear. That is, be attentive to spiritual things. Be ready to listen to what God may say to you (see on ch. 30:21). Be willing to know and to do the things He makes known to you.

Your soul shall live. That is, “you will live” (see on Ps. 16:10). None but those who respond to the appeal of vs. 1-3 and partake of Heaven’s bounties ever truly “enter into life” (Matt. 19:17). Only in Christ can men ever “have life” and “have it more abundantly” (John 10:10).

An everlasting covenant. All — Jew and Gentile alike (see Gal. 3:29; see on Isa. 55:1) — are invited to make the covenant relationship a reality in their own personal experience. This refers to the “new” covenant, under which God promises to write His law within men’s hearts (see on Jer. 31:31-34; Heb. 8:10, 11). This covenant embraces all the promises made to the fathers (Gen. 12:1-3; 17:7, 8; Ps. 89:3, 4, 28, 29, 36, 37; 105:8-12; see also pp. 26, 27).

Sure mercies of David. See p. 31. David was a great sinner. But when his sins were pointed out he repented sincerely and completely (see on Ps. 51), and accordingly became the recipient of divine mercy. This mercy is as “sure” for us today as it was for David.