John 14:10

Tertullian Against Praxeas

If, indeed, He meant the Father to be understood as the same with the Son, by saying, "He who seeth me seeth the Father," how is it that He adds immediately afterwards, "Believest thou not that I am in the Father, and the Father in me? "[339]

Tertullian Against Praxeas

And yet He omitted not to explain how the Father was in the Son and the Son in the Father. "The words," says He, "which I speak unto you, are not mine,"[341]

Alexander Epistles on the Arian Heresy

How, also, can He be changeable and mutable, who says indeed by Himself: "I am in the Father, and the Father in Me,"[54]

Dionysius Against the Sabellians

and, "I am in the Father, and the Father is in Me."[11]