法苑珠林 34.40

34.40

又惟無三昧經云。佛告阿難。善男子。人求道安禪先當斷念。人生世間所以不得道者。但坐思想穢念多故。一念來一念去。一日一宿有八億四千萬念。念念不息。一善念者亦得善果報。一惡念者亦得惡果報。如響應聲如影隨形。是故善惡罪福各別。

Also, the Weiwu sanmei jing says: The Buddha told Ānanda: "Good son, when a person seeks the Way and practises dhyāna, they must first sever thoughts. That people born in the world do not attain the Way is solely because they dwell in thinking and have many defiled thoughts. One thought comes, one thought goes; in a single day and night there are eight hundred and forty million thoughts, rising and ceasing without pause. A single good thought also obtains a good retribution; a single evil thought also obtains an evil retribution—like an echo answering a sound, like a shadow following a form. Therefore, good and evil, transgression and merit, are each distinct."