俱舍論疏 25.123

25.123

「論曰至任運轉故」，釋樂通也。通是道之別名。不多艱辛任運轉故，釋樂名也。《正理論》云「任運轉故，如乘船筏。」

"The Śāstra says: … because it proceeds spontaneously": this explains pleasant progress. Progress is an alternate name for path. Because it proceeds spontaneously without much hardship, this explains the name 'pleasant'. The Nyāyānusāra says: "Because it proceeds spontaneously, like riding a boat or raft."