佛說盂蘭盆經疏 2.73

2.73

淨業既成，必知離苦。觀因驗果聲響不差，故喜而止啼也。如處世刑獄，囑大力人，財賭既行其心已喜。

Since the pure karma was accomplished, he knew for certain that suffering would be left behind. Observing the cause confirms the fruit without the slightest discrepancy, like a sound and its echo; therefore he rejoiced and stopped weeping. It is like being imprisoned in worldly punishment: having entrusted oneself to a person of great power, once the wealth and bet are presented, one's heart is already joyful.