The Noble Mahāyāna Sūtra “Brahmā’s Question”

In the middle of the night, while the Buddha Śākyamuni is immersed in meditation, Brahmā, lord of the Sahā world, appears before him and asks him how bodhisattvas can quickly achieve full awakening. In response, the Buddha gives a teaching on mindfulness of the body. The following morning, when Brahmā has departed, the Buddha relays his teaching to the monks.