俱舍論頌疏論本 28.66

28.66

釋曰：初一行頌者，明淨等至總有四種：一順退分、二順住分、三順勝進分、四順決擇分。七地各四，有頂唯三，由彼處無上地可趣故，彼地無順勝進分。

The explanation says: The first verse line clarifies that the pure samāpatti has four kinds in total: first, the division concordant with falling away; second, the division concordant with maintenance; third, the division concordant with special progression; fourth, the division concordant with penetration. The seven stages each have four; the peak of existence has only three, because there is no higher stage to proceed to from that place; hence that stage lacks the division concordant with special progression.