When the Lord identifies these two things in the conversion of his people—the removal of ‘their heart of stone’ and the gift of ‘a heart of flesh’—he openly testifies that to turn us toward goodness everything which is of ourselves must be effaced, and that everything which takes its place must come from his grace. Nor does he declare this in one place only, for this is what we also read in Jeremiah: ‘I will give them one heart and one way, that they may fear me all their days; then I will put the fear of my name in their hearts, lest they turn away from me’ (Jer. 32:39–40). Again in Ezekiel: ‘I will give them all one heart, and I will create a new spirit in their inmost parts. I will take away their heart of stone and will give them a heart of flesh’ (Ezek. 11:19). He calls our conversion the creation of a new spirit and a new heart. Could he make it any plainer that the credit for what is good and upright in our will is properly his, not ours? It follows then that nothing good can ever come forth from our will until it is remade, and that, once remade, insofar as it is good, it is from God and not from us.
Accordingly we read of godly men who prayed prayers like that of Solomon: ‘May the Lord incline our hearts to himself, that we may fear him and keep his commandments’ (1 Kings 8:58). Here he reveals the stubbornness of our heart, declaring that it is naturally rebellious against God and his law, unless it is turned the other way round. Likewise does not David, in begging God to create in him ‘a new heart, and to renew a right spirit within him’ (Psa. 51:10) acknowledge that every part of his heart is full of filth and uncleanness, and that his spirit is enveloped in evil? Furthermore, in calling the purity he seeks a creation of God, he attributes it wholly to his power.
It is extraordinary that God demands of our pride nothing more onerous than that we observe his sabbath by resting from our labors. Yet there is nothing which we are more reluctant to do than to cease from all our works and to make room for his. Were it not for this obsession, nothing would stop us recognizing how fully the Lord Jesus attests to his gifts to us. ‘I am the vine,’ he says, ‘you are the branches, and my father is the vinedresser. As the branch cannot bear fruit of itself unless it abides in the vine, so it is with you, if you do not abide in me. For without me, you can do nothing’ (John 15:1, 4–5). Now if we cannot bear fruit of ourselves any more than a branch can which has been torn from the ground and deprived of all moisture, there is no point asking whether our nature is capable of doing good. Our conclusion can only be that without him, we can do nothing.
He does not say that we are so weak that we are unequal to the task. Instead, by stressing our utter insignificance, he rules out any notion that we have any power at all. If, once grafted into Christ, we bear fruit like a vine branch, which derives strength from the earth’s moisture, from the dew of heaven and the warmth of the sun, it seems to me that we are left with no share in good works of any kind—provided we wish to reserve all honor for God.
– Institutes of the Christian Religion, 2.3.8–2.3.9 (Trans. Robert White)