Ephesians 3:16

That he would grant you, according to the riches of his glory, that ye may be strengthened with power through his Spirit in the inward man.

The inward man ... Clarke's definition of the "inward man" is as good as any. He wrote:

Every man is a compound being, having a body and a soul. The outward man is that alone which is seen and considered by men. The inward man is that which stands particularly with reference to God and eternity.[34]

All of the Ephesians whom Paul had converted had been made partakers of the Gift Ordinary of the Holy Spirit, granted to them as an earnest of their redemption at the time they were baptized into Christ (see Acts 2:38,39; Ephesians 1:13). The prayer in this verse is to the effect that the Spirit of God within them would be a source of power, more firmly establishing them in the faith.

Wedel spoke of the confusion and uncertainty many feel with regard to such a thing as the "indwelling" Spirit of God thus:

The concept of the Holy Spirit is at best vague in popular understanding; and even theologians can be puzzled by such phrases as are in this verse ... And the expression, "Christ may dwell in your hearts" (next verse) can be equally puzzling.[35]

See extended remarks on this problem under Galatians 5:23, above. There are no less than eight designations for the same Scriptural phenomenon, two of them being in these verses of 16,17.

[34] Adam Clarke, Commentary on the Holy Bible (London: Carlton and Porter, 1829), Vol. VI, p. 447.

[35] Theodore O. Wedel, The Interpreter's Bible, Vol. X. (Nashville: Abingdon Press, 1953), p. 676.