143. The production of those virtues is the province of the Holy Spirit, whom the Lord sends to those who believe in Him and make themselves fit to receive Him. This is what is meant by the Spirit in these and other passages:
I will give you a new heart and a new spirit, I will put my spirit within you, and make you walk according to my statutes*. Ezek. 36:26, 27; 11:19.
Create a clean heart in us, o God, and make new a steadfast spirit within me. Bring back to me the joy of your salvation, and let the Spirit which acts of its own accord uphold me. Ps. 51:10, 12.
Jehovah forms the spirit of man within him. Zech. 12:1.
With my soul I have waited for you by night, and with my spirit within me I have waited for you in the morning. Isa. 26:9
Make yourselves a new heart and a new spirit. Why will you die, o house of Israel? Ezek. 18:31.
In these passages a new heart means the will to do good, and a new spirit the understanding of truth. It is clear from what it says there that the Lord effects these things with those who do good and believe the truth, that is, those who have the faith of charity, when it says that God gives breath to those that walk according to His statutes*, and that it is called 'the Spirit which acts of its own accord.' It is clear that man must take action on his own side from the words, 'Make yourselves a new heart and a new spirit. Why will you die, o house of Israel?'
* The Latin has 'in the way of salvation', but this is corrected in the author's copy.