俱舍論頌疏論本 3.33

3.33

餘處此名喜者，除第三禪，於下三地名為餘處（下三地者，欲界、初、二禪也）。此者，此第六識心也，謂此心悅於下三地名為喜根。第三靜慮心悅安靜，離喜貪故，唯名樂根。下三地中心悅麁動，有喜貪故，唯名喜根。

"Elsewhere, this is called gladness" means: excluding the third dhyāna, in the lower three stages it is called "elsewhere" (the lower three stages are the desire realm, the first dhyāna, and the second dhyāna). "This" refers to this mind of the sixth consciousness; that is to say, the pleasure of this mind in the lower three stages is called the gladness faculty (saumanasyendriya). In the third dhyāna, mental pleasure is tranquil and serene because it is separated from the craving for joy; therefore, it is exclusively called the pleasure faculty. In the lower three stages, mental pleasure is coarse and active because there is craving for joy; therefore, it is exclusively called the gladness faculty.