‘I say this so that no one may (or ‘let no one') delude you with persuasive speech, for though I am absent in the flesh, yet I am with you in the spirit, full of joy and beholding your order and the steadfastness of your faith in Christ.'
His purpose in showing them the supremacy of Jesus Christ, and that all worthwhile wisdom and knowledge are found in Him, was in order to combat those who came among them with persuasive words. For although he cannot be with them in body, yet he is truly among them in spirit (compare the use in 1 Corinthians 5:3-5), genuinely concerned for them, full of joy at their ‘orderly behaviour' (we could translate this as ‘closing of ranks', another use of the Greek word, as they unite against those who would deceive them), their growth and the steadfastness of their faith in Christ. He wants them to know that although he has never himself been there, Epaphras has given him a full picture of what they are, so that his affection for them is genuine.
‘Flesh -- spirit'. A common contrast in Paul's letters. But here ‘flesh' is not used in its Pauline sense as signifying the part of us that drags us down. It signifies being human (as in John 1:14). And when the ‘spirit' of a Christian is spoken of the Spirit is not far away. He may therefore mean, or include, the idea of ‘by the Spirit' (compare Galatians 3:3 where the Spirit is contrasted with the flesh).
‘Order.' This could mean orderly behaviour in the family (compare 1 Corinthians 14:40) or could refer to military order, closing ranks against the enemy.
‘Steadfastness.' The word can mean a ‘barrier'. Thus he may be saying that they have closed ranks and set up a barrier against the foe, the barrier of faith (compare ‘the shield of faith' - Ephesians 6:16). But the idea may be more generally of steadfastness of faith.
Christ Who Partakes In All The Fullness of God Has Saved, Transformed and Delivered Us (Colossians 2:6 - Colossians 2:15)