If you offer fasting with humility and with mercy, your bones, as Isaiah said, shall be fat, and you shall be like a well-watered garden (cf. Isa. 58:11). So, then, your soul shall grow fat and its virtues also by the spiritual richness of fasting, and your fruits shall be multiplied by the fertility of your mind, so that there may be in you the inebriation of soberness, like that cup of which the Prophet says: 'Your cup which inebriates, how excellent it is' (Ps. 23:5 LXX)!
AmbroseIf you are at Rome live in the Roman style; if you are elsewhere live as they live elsewhere.
Ambrose... these three witnesses are one, as John said: 'The water, the blood, and the Spirit' (I Jn. 5:8). One in the mystery, not in nature. The water, then, is a witness of burial, the blood is a witness of death, the Spirit is a witness of life. If, then, there be any grace in the water, it is not from the nature of water, but from the presence of the Holy Spirit.
AmbroseThe Church was redeemed at the price of Christ's blood. Jew or Greek, it makes no difference; but if he has believed, he must circumcise himself from his sins [in baptism (Col. 2:11-12)] so that he can be saved . . . for no one ascends into the kingdom of heaven except through the sacrament of baptism . . . "Unless a man be born again of water and the Holy Spirit, he cannot enter the kingdom of God"
Ambrose