Children and Heirs of God
The Spirit here is of course the Holy Spirit, by whom Christ our Lord lives within us. It is passing wonderful that as the life which throbs in the heart beats also in the pulse, so the very life which is in Christ in glory is also in our hearts. Our main task is to put aside every barrier to its full expression. This is what the Apostle means by doing to death the practices, stratagems, and lawless promptings of the body, which are ever calling for ease and self-indulgence. There is no stage of our earthly pilgrimage at which we can dispense with the power of the Spirit of God for deliverance from the deeds of the body.
But there is another most blessed function of the divine Spirit, Romans 8:14. He is willing to lead us, to prompt our actions, to inspire our purposes, and to mold our characters. The more we yield to Him, the deeper becomes our awareness of that filial relationship with God which breathes in the cry, Abba, Father. But note the wonderful climax, Romans 8:17. If we yield to the Holy Spirit, He will conduct us into the divine treasure-house and bid us avail ourselves of the infinite resources which are there stored for our use, not in the next life, but in this.