釋禪波羅蜜次第法門 2.142

2.142

Fifth, singleness of mind: the practitioner has already become proficient in deliberating with skillful wisdom and applies his mind without error; now he need only focus his mind, maintain oneness, and practice; hence it is called singleness of mind. Just as when a person wishes to travel for good purpose, he must recognize which paths are open and which blocked, and having determined this, sets out with singleness of mind. Thus it is said that without wisdom there is no dhyāna, and without dhyāna there is no wisdom; the meaning lies here.