The word "wherefore" at the beginning of this, the second part of the chapter, indicates that Paul is drawing some conclusions from that which he has stated in the previous verses. He had already reminded them in the earlier verses, of their spiritual state before the grace of God delivered them. He was now going to reinforce those memories.
I. REMEMBERING OUR FORMER STATE IS AN ESSENTIAL EXERCISE FOR THE CHILD OF GOD.
1. How quickly we forget God's merciful dealings with us. James 1:23-24. We are not inclined to retain spiritual impressions. In Egypt, Israel's circumstances were terrible, Exodus 2:23-25; 3:7. But once delivered, they soon forgot, Ex 16:1-3. This was but four weeks later!
So it is still with God's people. Gal 1:6. They had turned away from the gospel, having forgotten what it had done for them. This church at Ephesus was to do the same, despite Paul's exhortations here, Rev 2:4.
2. Such forgetfulness leads to great sin. It is the seed-bed of all rebellion. "The wicked shall be turned into hell, and all the nations that forget God," Psalm 9:17. It is the basis of apostasy, Rom 1:28. "And it shall be, if thou do at all forget the LORD thy God, and walk after other gods, and serve them, and worship them, I testify against you this day that ye shall surely perish," Deut 8:19. Job 8:11-13. Gal 4:9; 2 Pet 1:9-15.
3. God repeatedly commands remembrance of His dealings with us. "And remember that thou wast a servant in the land of Egypt, and that the LORD thy God brought thee out thence through a mighty hand and by a stretched out arm: therefore the LORD thy God commanded thee to keep the sabbath day," Deut 5:15. "And thou shalt remember all the way which the LORD thy God led thee these forty years in the wilderness, to humble thee, and to prove thee, to know what was in thine heart, whether thou wouldest keep his commandments, or no," Deut 8:2.
There is a "looking back" that is essential to our wellbeing. "Hearken to me, ye that follow after righteousness, ye that seek the LORD: look unto the rock whence ye are hewn, and to the hole of the pit whence ye are digged. Look unto Abraham your father, and unto Sarah that bare you: for I called him alone, and blessed him, and increased him," Isaiah 51:1-2. "Ye know that ye were Gentiles, carried away unto these dumb idols, even as ye were led," 1 Cor 12:2.