妙法蓮華經玄贊 7.431

7.431

贊曰：第四大段佛默然許。問：何故涅槃時默然不受他供，今者默然遂許他說？古解以佛顏有舒𣫍，請者覺許、不許。又云以佛身光表知受與不受。又云佛初成道時自唱號言「凡時默然受請，涅槃時默然是不受請」。又受食理須呪願，默然知佛不許。許說默已順請，不假出言而許。

The Commentary says: The fourth major section is the Buddha's silent consent. Question: Why at the time of nirvāṇa did he remain silent and not accept others' offerings, whereas now by remaining silent he consents to their request to preach? Ancient commentators explained that the Buddha's facial expression showed joy or displeasure, so the requester could discern whether consent was given or not. It is also said that the radiance of the Buddha's body manifests whether he accepts or does not accept. It is also said that when the Buddha first attained enlightenment, he himself proclaimed: 'In ordinary times, silence indicates acceptance of requests; at the time of nirvāṇa, silence indicates non-acceptance of requests.' Furthermore, accepting food properly requires incantation and prayer, so by remaining silent one knows the Buddha does not grant it; whereas consenting to preach by silence already accords with the request, not needing spoken words to grant it.