坐禪三昧經 2.6

2.6

These two things, initial thought and sustained thought, disturb the mind in dhyāna concentration. Just as clear water is muddied when agitated by waves, so the practitioner, having already attained one-pointedness within, is distressed by initial and sustained thought; [eliminating them is] like gaining rest when exhausted, like finding peace in sleep. At that time, in sequence, free of initial thought and sustained thought, pure concentration is born, with internal clarity, joy, and bliss, and he attains entry into the second dhyāna.