Here the effect of delight in righteousness that it broadens, widens, the heart. Notice, once again, the invocation of Rom 5:5, so important in Augustine’s theology of grace. Our ability to love God, our loving God, is itself the gift of God who thus gives what he commands.
“I ran the way of your commandments,” he says, “when you broadened my heart” (Ps 118:32)–not, then, by myself without any need of your help, but “when you broadened my heart.” Hearts are broadened when they delight in righteousness. This is a gift of God: our not being narrowed by fear of punishment, but broadened by love and by delight in righteousness. He promised this broadness when he said, “I will dwell in them and walk about among them” (2 Cor 6:16). How broad must the place be where God walks about! For this broadness, “love has been spread abroad into our hearts by the Holy Spirit who has been given to us” (Rom 5:5). That’s why it is also said, “Let your waters run freely in your streets” (Prov 5:16).... These are the waters of which the Lord cried out: “Let him who is thirsty come to me. Whoever believes in me, rivers of living water will flow from his belly,” and the Evangelist explains what he said: “He said this of the Spirit which they who believed in him were to receive” (Jn 7:37-39). (EnPs 118/10, 6; PL 37, 1527).
When the Psalmist says, “Your command is exceedingly broad” (Ps 118:96), I think he must be speaking of love.... “The love of God has been spread abroad in our hearts by the Holy Spirit who has been given to us” (Rom 5:5). Broadness consists in this broad spreading of love by which we can walk without narrowness even on a narrow path, and this by God’s gift “who has broadened my steps beneath me, and my footprints have not been weakened (Ps 17:37). Broad, then, is the command to love, that twin command, by which we are commanded to love God and neighbor. What could be broader than that on which depends the entire law and all the prophets? (EnPs 118/21, 9: PL 37, 1561-62)