金剛經纂要刊定記 4.320

4.320

一往等者。以九品修惑，能潤欲界七生。謂上上品潤兩生，次三各一生，次二品共一生，下三品共一生。今斷六品已損六生，猶殘下三品潤欲界一生，是故一往天上，更須一來人間受生，斷餘惑也。

"Going once, etc.": because the nine grades of afflictions of cultivation can moisten seven rebirths in the desire realm. That is, the highest-of-high grade moistens two rebirths, the next three each moisten one rebirth, the next two grades together moisten one rebirth, and the lowest three grades together moisten one rebirth. Now, having severed six grades, six rebirths are already diminished; there still remain the lower three grades moistening one rebirth in the desire realm, which is why going once to heaven, they must once more come to the human realm to take rebirth and sever the remaining afflictions.