St. Augustine had a deep spiritual life and left us many profound prayers.
Here is a prayer attributed to St. Augustine for the indwelling of the Holy Spirit.
Holy Spirit, powerful Consoler, sacred Bond of the Father and the Son, Hope of the afflicted, descend into my heart and establish in it your loving dominion. Enkindle in my tepid soul the fire of your Love so that I may be wholly subject to you. We believe that when you dwell in us, you also prepare a dwelling for the Father and the Son. Deign, therefore, to come to me, Consoler of abandoned souls, and Protector of the needy. Help the afflicted, strengthen the weak, and support the wavering. Come and purify me. Let no evil desire take possession of me. You love the humble and resist the proud. Come to me, glory of the living, and hope of the dying. Lead me by your grace that I may always be pleasing to you. Amen.