Yoga Sutras 1.23-1.29: Contemplation on AUM (or OM).

OM is a direct path: Remembering the sound vibration of AUM (or OM), along with a deep feeling for the meaning of what it represents (1.28), brings both the realization of the individual Self and the removal of obstacles that normally block that realization (1.29). In a sense, this practice is like a short cut, in that it goes directly to the heart of the process.

Systematically piercing the levels: This practice takes one on a direct route inward, systematically piercing the levels of consciousness. It is done with sincerity and dedication (1.23) towards the untainted creative source or pure consciousness (1.24), which AUM represents (1.27). That consciousness contains the seed of omniscience (1.25), which is the source of the teachings of all the ancient sages (1.26).

Remember the meaning: For it to have its effect, the sound of AUM is remembered with deep feeling for the meaning of what it represents. (1.28)

https://swamij.com/yoga-sutras-12329.htm