Ambrose of Milan

Having received the sacraments, you have fully understood everything that you were baptized in the name of the Trinity. In all that we have done, the mystery of the Trinity has been preserved. Everywhere, there is the Father and the Son and the Holy Spirit, one operation, one sanctification, although some things may seem special. How? God who anointed you, and sealed you, and placed the Holy Spirit in your heart. Therefore, you have received the Holy Spirit in your heart.