Master Feixi’s 飛錫 Gaosheng nianfo sanmei baowang lun 高聲念佛三昧 寶 王論 (Precious King’s Treatise on the Samādhi Gained by Loudly Invoking the Buddha’s Name) states:

"Those who bathe in the ocean are making use of hundreds of rivers.

Those who invoke the Buddha’s name must have mastered samādhi.

Like a water-purifying gem placed in cloudy water, the cloudy water cannot but become clear; so too, when recollection of the Buddha is introduced into the distracted mind, the distracted mind cannot but become a buddha.

After these tally with one another, mind and buddha will both disappear.

Their mutual disappearance is samādhi; their mutual radiance is prajñā.

Since samādhi and prajñā are balanced, what mind is not buddha and what buddha is not mind?

Once mind and buddha are just so, there then are none of the myriads of sensory objects and myriads of conditions that are not samādhi."

Zen Master Chinul then said, "Who would want to disturb this [state] any further by stirring up the mind and activating thoughts through loudly invoking the Buddha’s name?"