法苑珠林 11.61

11.61

又智度論云。佛成道已不即說法。於五十七日。今撿括機緣然後說法。初七日思大乘法化。第七七日用於小乘以擬眾生。

Furthermore, the Mahāprajñāpāramitā-śāstra states: After the Buddha attained the Way, he did not preach the Dharma immediately; for fifty-seven days, he carefully examined the conditions of capacities, and only then did he preach the Dharma. During the first seven days, he contemplated delivering beings through the Mahāyāna Dharma; during the seventh seven days, he applied the Hīnayāna to adapt to sentient beings.