Ambrose of Milan

Abraham, ready to receive strangers, faithful towards God, devoted in ministering, quick in his service, saw the Trinity in a type; he added religious duty to hospitality, when beholding Three he worshipped One, and preserving the distinction of the Persons, yet addressed one Lord, he offered to Three the honour of his gift, while acknowledging one Power. It was not learning but grace which spoke in him, and he believed better what he had not learnt than we who have learnt. No one had falsified the representation of the truth, and so he sees Three, but worships the Unity. He brings forth three measures of fine meal, and slays one victim, considering that one sacrifice is sufficient, but a triple gift; one victim, an offering of three.