Only a faith working through love, from heavenly charity, gives a good work
Nor does he think an inert and idle faith is enough for someone to be able to act morally well. He holds that an active faith is required, one that in some way works through love. For he does not think any work is morally good, or escapes the character of sin, unless it proceeds from the love of God and from a kind of heavenly charity.
This is seen especially in chapter 16 of the third book already cited, On the state of fallen nature. There he sets out to teach from Augustine that no good work, that is, no work without sin, can be done by man unless the good deed itself is loved: that is, unless the righteousness of the precept itself delights the mind. For him, to delight in the righteousness of the precept is nothing other than to pursue a good work out of heavenly charity, since God is righteousness, and righteousness is loved by charity alone. So to do good by loving the righteousness of the law is nothing other than to do good by loving God himself with the charity of the Holy Spirit, because God is righteousness itself and truth.
So, in Augustine's own words, he affirms that there is no good fruit that does not spring from the root of charity, and that only then, and not otherwise, does anyone begin to delight in the righteousness of the law, when the faith that works through love is present. In chapter 16 of the next book he teaches that faith is needed for a good work because it is faith that obtains the help to love God. There too he affirms that there is no good work and no good will except from the intention of a good faith, that is, of the faith that works through love.
Latin
XXXVI. Nec ad hoc ut quis bene moraliter operari possit, sufficere censet fidem inertem atque otiosam, sed requiri putat fidem actuosam, & quae sit aliquo modo per dilectionem operans. Non existimat enim ullum opus esse moraliter bonum, & effugere rationem peccati, quod non ex amore Dei & coelesti quadam charitate procedit. Illud praesertim videre est capite decimo sexto libri tertii jam citati, De statu naturae lapsae. Ubi ex Augustino docere aggreditur nullum opus bonum, hoc est, sine peccato, fieri ab homine posse, nisi ipsum benefactum diligatur: id est, nisi ipsa justitia praecepti delectet animum. Ipsa vero praecepti justitia delectari, ipsi non est aliud, quam opus bonum ex coelesti charitate prosequi: quoniam Deus justitia est, nec illa, nisi sola charitate diligitur. Et sic justitiam legis diligendo benefacere, non est aliud quam Deum ipsum charitate Spiritus Sancti diligendo, benefacere: quia Deus est ipsa justitia & veritas. Adeoque verbis ipsis Augustini affirmat nullum esse fructum bonum, qui de charitatis radice non surgit. Et tum demum, ac non aliter, aliquem incipere justitia legis delectari, quum adest fides quae per dilectionem operatur. Capite vero decimo sexto libri sequentis, ideo fidem ad bonum opus necessariam esse docet, quia ipsa est quae auxilium ad Deum amandum impetrat. Ibidemque affirmat nullum bonum opus, & nullam bonam voluntatem esse, nisi ex intentione fidei bonae, id est, ejus quae per dilectionem operatur.