The following verses are taken from the first chapter of the Yoga Sutras, written by or ascribed to Patanjali.  Almost nothing is known about the author; even the dates of the composition of the Yoga Sutras are uncertain, sources suggesting any time from the 5th c. BCE to the 4th c. CE.  Nevertheless, the sutras are fundamental to classical yoga.  These verses speak of the clearing of the mind through  contemplation on ‘Om,’ the sacred seed syllable, which Sufis find to be identical with ‘Hu,’ the vibration of the all pervading Presence, and the fixing of the mind in concentration.

From this [repetition and contemplation the meaning of the mystical syllable Om] comes the realisation of the inner consciousness and freedom from all disturbances.

These disturbances are disease, idleness, doubt, carelessness, sloth, lack of detachment, misapprehension, failure to attain a base for concentration, and instability. They are distractions for the mind.

Suffering, dejection, trembling, inhalation, and exhalation accompany the distractions.

Practice of fixing the mind on one object should be performed in order to eliminate these disturbances.

By cultivating an attitude of friendship toward those who are happy, compassion toward those in distress, joy toward those who are virtuous, and equanimity toward those who are nonvirtuous, lucidity arises in the mind.

Tr. Edwin F. Bryant