As the Buddha sat under the Ajapāla Banyan tree, soon after the Enlightenment (in the fifth week, says the Commentary, S.A i.158), a thought came to him that he should have someone whom he could consider and honour as his teacher. But, seeing no one worthy of such honour and respect, he decided that the Dhamma should be his teacher. Thereupon Sahampati appeared before him and reminded him that in this decision he was acting as all Buddhas acted. S.i.138f.