佛說觀佛三昧海經 9.4

9.4

佛告阿難：「如來往昔無量無邊阿僧祇劫，以智慧火燒煩惱薪，修無相定不非時證，是故獲得如是勝相，一一相中無量化佛，何況多相？若能係心觀一毛孔，是人名為行念佛定。以念佛故，十方諸佛常立其前，為說正法，此人即為能生三世諸如來種，何況具足念佛色身？

The Buddha told Ānanda: “In the past, for immeasurable, boundless asaṃkhyeya kalpas, the Tathāgata burned the fuel of afflictions with the fire of wisdom and cultivated signless samādhi without prematurely realising it. Therefore, he obtained such supreme marks, with immeasurable transformation Buddhas within each mark—how much more so within many marks! If one can focus the mind to contemplate a single hair-pore, that person is called one who practices the samādhi of mindfulness of the Buddha. Because of mindfulness of the Buddha, the Buddhas of the ten directions will constantly stand before them and expound the true Dharma for them. Such a person will be capable of generating the lineage of all the Tathāgatas of the three times—how much more so if they fully contemplate the Buddha's form-body?