What is the relationship between Colossians and Ephesians?

Answer
Colossians is generally considered somewhat earlier than Ephesians, in which many passages echo Colossians. Of the 155 verses in Ephesians, 75 have verbal parallels in Colossians, but not as simple imitation or copying, as for example between 2 Peter and Jude. The parallels are numerous but subtle. Some of the similarities follow:

Twenty one Words are found in both Colossians and Ephesians but nowhere in Paul's own letters. Colossians 1:1-2 and Ephesians 1:1-2; Colossians 1:25 and Ephesians 3:2; Colossians 1:26 and Ephesians 3:9 each have 7 consecutive Words the same. Five identical, consecutive Words occur in Colossians 1:14 and Ephesians 1:7; Colossians 2:9 and Ephesians 4:16.

Ephesians 6:21-22 is identical (in Greek) to Colossians 4:7-8.

Colossians 4:5 "Walk in wisdom toward them that are without, redeeming the time." Ephesians 5:16 "Redeeming the time, because the days are evil." Both passages use the same unusual phrase, which does not occur anywhere else in The Bible.

Colossians 3:5 "Mortify therefore your members which are upon the earth; fornication, uncleanness, inordinate affection, evil concupiscence, and covetousness, which is idolatry:" Ephesians 5:5 "For this ye know, that no whoremonger, nor unclean person, nor covetous man, who is an idolater ..." Here, the Wording of Ephesians looks much different, but on closer inspection it contains the same vices stated in the same order, without Colossian's emphatic repetition of 'fornication' (inordinate affection, evil concupiscence).