Canonical Reference: Dhp 2 Verified Source

“Mind precedes all mental states. Mind is their chief; they are all mind-wrought. If with a pure mind a person speaks or acts, happiness follows him like a never-departing shadow.”

— Gautam Buddha
The Awakened One, Founder of Dhamma
Historical Setting & Context:

Pali Canon: Dhammapada 1.2 (Manopubbaṅgamā dhammā manoseṭṭhā manomayā...).