God’s working in us is not suspended because we work, nor our working suspended because God works. Neither is the relation strictly one of cooperation as if God did his part and we did ours so that the conjunction or coordination of both produced the required result. God works and we also work. But the relation is that because God works we work. All working out of salvation on our part is the effect of God’s working in us...We have here not only the explanation of all acceptable activity on our part but we also have the incentive to our willing and working...The more persistently active we are in working, the more persuaded we may be that all the energizing grace and power is of God.
John Murray
20th century Scottish Theologian