51:1-2 The prophet called to the righteous among God’s people and reminded them of their heritage. Abraham was the rock from which the people of God were cut and Sarah the quarry from which they were dug. From the one man came many descendants, according to the promise of the Abrahamic covenant (Gn 12:1-3).
51:3 On the foundation of the ancient promises to Abraham, God will transform Zion’s suffering and devastation (her wilderness . . . her desert) to joy and prosperity (Eden . . . garden of the Lord).
51:4-5 According to the Abrahamic promise, his descendants were to be a blessing to the nations. The coasts and islands represent the distant nations (49:1). Invoking them implies that all the nations of the world will put their hope in the Lord.
51:6 From a human perspective the heavens and the earth look permanent. People die but the heavens and earth endure. But God’s salvation and righteousness make even the heavens and the earth appear temporary.
51:7-8 If the heavens and the earth are temporary, so are even shorter-lived humans. Why then should any individual fear another? The only one who is the proper recipient of our fear is the Lord himself.
51:9-10 God is encouraged to wake up from slumber and go about his redemptive work (Ps 44:23; 78:65). Past victories are then recounted in the form of the defeat of Rahab, a sea monster (see 30:7; Jb 26:12; Ps 89:10). The sea and its monsters represent the forces of chaos that are against God and his creation. Rahab in other texts clearly stands for Egypt. Here we have a poetic allusion to God’s victory over the Egyptians at the time of the exodus. God, after all, dried up the sea-bed and made it a road at the Red Sea (Ex 14-15). God’s past deliverance of his people from Egyptian bondage bodes well for their future deliverance from Babylonian captivity.
51:11 This verse proclaims the new exodus (from Babylon).
51:12 It is folly to fear humans who die rather than the Lord who endures forever.
51:13 God constructed the heavens and the earth like a person would build a tent (stretched out) or a house (laid the foundations).
51:14 The word prisoner refers to those who were exiled by the Babylonians. Some high-ranking officials were literally thrown into prisons (2Kg 25:27), but others were in a metaphorical prison by being removed from their land and forced to live in Babylon. The Israelites thought of the grave and the underworld as a large Pit.
51:15 God is in charge of the mighty waters. This shows metaphorically his ability to control the forces of evil.
51:16 According to Motyer (TOTC), this verse is about the servant who would be kept hidden until the proper time.
51:18 In the ancient Near East, it was the duty of the children to care for a drunk parent. Noah’s son Ham acted in a reprehensible manner when his father was drunk (Gn 9:18-29). Here Jerusalem’s children, God’s people, did not take hold of her hand when she was drunk after drinking the cup of God’s fury.
51:21-23 Once Jerusalem has experienced the full force of God’s judgment, once they have drunk of the cup of his fury, he will take it away and give it to their tormentors. Among the latter, Babylon is particularly in mind.