Luke 17:21

Tertullian Against Marcion Book IV

This means, "Neither in this place nor that place is the kingdom of God; for, behold, it is within you."[1423]

Hippolytus Refutation of All Heresies Book V

But they assert that not only is there in favour of their doctrine, testimony to be drawn from the mysteries of the Assyrians, but also from those of the Phrygians concerning the happy nature-concealed, and yet at the same time disclosed-of things that have been, and are coming into existence, and moreover will be,-(a happy nature) which, (the Naassene) says, is the kingdom of heaven to be sought for within a man.[32]

Hippolytus Refutation of All Heresies Book V

This, says he, is the kingdom of heaven that reposes within us as a treasure, as leaven hid in the three measures of meal.[78]

Cyprian Treatise XII Three Books of Testimonies Against the Jews

Also in the Gospel according to Luke: "The kingdom of God is within you."[631]

Peter of Alexandria Canonical Epistle

Moreover, we hear both also preaching, in the first place, not only repentance, but the kingdom of heaven, which, as we have learned, is within us;[15]

Origen Commentary on Matthew Book X

if not in idea, manifestly to those to whom it is said, "The kingdom of God is within you,"[73]

Origen Commentary on Matthew Book XII

is to be referred, not to the time, but to deeds and dispositions; for Christ, who is all virtue, has come, and speaks, and on account of this the kingdom of God is within His disciples, and not here or there.[104]