New Defender's Study Bible Notes
51:1 whence ye are hewn. It is salutary for God’s people to remember the background out of which the Lord called them to Himself, not to reflect on old sins, but to renew a thankful heart for what He has done for them.
51:3 wilderness like Eden. Isaiah here not only confirms the historicity of the garden of Eden, but also confirms that all its perfections will one day be restored: God does not fail in His purposes.
51:6 wax old like a garment. This is an anticipation of the scientific law of increasing entropy. The heavens, the earth, and all things are in a process of decay and ultimate death, but God’s salvation and righteousness shall never die. See also Psalm 102:25-27.
51:9 Rahab. God’s power was greatly manifest in the “ancient days,” especially in the days of Noah and Moses, and perhaps even more so when Satan, that old “dragon” was cast out of heaven. The name “Rahab” is enigmatic. It does not refer to the harlot of Jericho (Joshua 2) but to a great enemy of God (see also Psalm 87:4; 89:10). “Rahab” means “boaster” and could well be—in this context, at least—a name for “the dragon.” However, many scholars assume it refers to Egypt.
51:11 everlasting joy. This glorious promise of kingdom blessing is directed primarily to Israelites redeemed during the tribulation and entering the millennial kingdom still living on earth (see notes on Matthew 25:34,40). Indirectly it also includes all the redeemed of all ages as they enter the eternal kingdom in the New Jerusalem (Revelation 21:1-7).