佛說觀佛三昧海經 4.26

4.26

The Buddha told Ānanda: "After the Buddha’s parinirvāṇa, if the Buddha’s disciples see the light of the mark on the Buddha's chest, they will eliminate the sins of birth and death of twelve myriad koṭis of kalpas. If they cannot see the mark on his chest clearly, they should enter a stūpa to contemplate it. Such contemplation is called correct contemplation; if one contemplates otherwise, it is called false contemplation."