„God is only where you let Him in.“
As quoted in Innerspace : Introduction to Kabbalah, Meditation and Prophecy (1990), by Aryeh Kaplan, p. 160; This expression is said to have originated when he was five years old and asked his father "Where is God?" to which his father answered: "God is everywhere!" Rebbe then responded "No, I think God is only where you let Him in."
Variants:
Where is God to be found? In the place where He is given entry.
As quoted in The Sayings of Menahem Mendel of Kotsk (1995) by Simcha Raz and Edward Levin, p. 10
God is where you let Him in.
As quoted in Everyday Kabbalah: A Practical Guide to Jewish Meditation, Healing, and Personal Growth (1998)