Laotzu's Heart Realization Classic 太上老君说了心经

The author is unknown. Judging from its content, it was presumably compiled during the Tang Dynasty.

Consisting of one volume, it is included in the Ben Wen (Original Text) category of The Dongshen Section in The Daozang.

The scripture expounds the method of internal observation to understand the mind. It proclaims: "The mind is the master of the spirit; movement and stillness originate from the mind"; "To cultivate the Dao, one must first observe one’s own mind." The method of observing the mind lies in "neither moving nor being still, neither thinking nor retaining." Be mindless and motionless; if there is motion, let it arise from the mind. Understand the true nature of the mind, and understand the mind of true nature. The mind abides nowhere, and where it abides, there is no mind. Be free from attachment and clinging; without clinging, one transforms into truth. Emptiness has no abode of emptiness; in the abode of emptiness, one realizes truth."

Its theories are derived from the Chongxuan (Double Mystery) philosophy of Taoism in the Sui and Tang dynasties.