Probably, the most profoundly direct instruction Christ gave concerning the teaching of non-dualism is from
"The light of the body is the eye: Therefore, when thine eye is single, your whole body will be filled with light...." (Luke 11: 34)
This non-dual teaching is easily paraphrased as follows: The part of you that sees (the seer, one's Self) is your true light. Therefore, if you hold to (i.e., abide as) the seer (subject-"I") singlely or exclusively (i.e., relinquishing attention to thoughts) you will have illumination - or what some call the "enlightenment of the whole body". This is the exact instruction given in the non-dual Vedanta tradition, with the same described outcome, as related above.
See the the Non-Dual Christ Consciousness described in the Vedic Verse
and Avadhut Gita verse below, very similar to the above records:
Vedic Verse -- Atharva Veda, Mundaka Upanishad 2.2.9:
In the highest golden sheath is the Godhead, unsullied, indivisible; pure is it, the Light of lights. He who knows the Self knows it. Neither sun nor moon nor stars shine there. Neither lightning nor fire finds there a place. With the radiance of that Light alone all things shine. That radiance illumines all this world.
Song of the Ever free -- Avadhuta Gita (Chapter 7 Verse 4):
In this state of realization, how can the Avadhuta
consider whether he has a body or not,
or whether he has attachment or not?
He himself is the immaculate, immovable, innate Reality
-infinite as space.
Pieter Schoonheim Samara is author of The Self, Maya, and the Heart: The Fundamentals of Non-Dualism