金剛經纂要刊定記 5.142

5.142

而樂者。然有四意故樂：一、為忍熟故樂，如役力之人久得其志也。二、為正定故樂，常踞大定寂滅不動故。三、為慜他故樂，如孩子杖父父即樂生。四、為自利故樂，以將此幻形易得堅質。具茲四意，故言樂也。疏文但有前三。

"And joyful": There are four reasons for being joyful: 1. Joyful because forbearance is mature, like a labourer who after a long time achieves his purpose. 2. Joyful because of right concentration, because one constantly abides in great absorption, tranquil and unmoving. 3. Joyful out of pity for others, like when a child strikes its father, the father feels joy arising. 4. Joyful for one's own benefit, because using this illusory form one easily attains an enduring substance. Possessing these four intentions, it is therefore said to be joyful. The commentary text contains only the first three.