21 In Him the whole structure is joined (bound, welded) together harmoniously, and it continues to rise (grow, increase) into a holy temple in the Lord [a sanctuary dedicated, consecrated, and sacred to the presence of the Lord].22 In Him [and in fellowship with one another] you yourselves also are being built up [into this structure] with the rest, to form a fixed abode (dwelling place) of God in (by, through) the Spirit.
Through Christ, we are joined together in harmony. The Lord purifies us into a holy temple in the Lord so that we are dedicated and set apart unto Him. We form a fixed dwelling place of God through the Spirit.
A fixed dwelling place for God. This says that as we are joined together with other believers, God is able to dwell among us. This does not mention that we can have God dwell among us alone, but that as we have fellowship with other believers, we are being built up to form this place where God dwells. It seems apparent that it is vital for us to be in fellowship with other believers.
V21 speaks of the way that we are joined together in harmony to form a place where God can dwell. V22 then talks about us being joined together with one another, but not only the group as it is through God that this occurs.