After a stay in Vesali, Shakyamuni and Ananda went northward to the village of Bhanda, then to Hatthi, Amba, Jambu, and then out of the kingdom of the Vajjis to Bhoga, in the land of the Mallas, where, at the Ananda shrine, Shakyamuni preached on the topic of the Four Great References. According to this sermon, the members of the Order are instructed to be critical of all reported teachings; to examine them diligently; to compare them with the scriptures and the genuine teachings; and, on the basis of such comparison, to decide whether they are true. Four kinds of reports to be subjected to such inquiry are cited: words reported as having been heard directly from Shakyamuni himself, words reported as having been heard from a group of elders, words reported as having been heard from several elders, and words reported as having been heard from a single elder. Monks must not accept blindly what has been said but must examine it on the basis outlined above. Today, too, it is important to investigate what is offered as truth in the light of the counsel of trustworthy leaders and authoritative scriptures before accepting it as true. Buddhists are taught to compare an opinion with teachings, reason, and actuality to determine whether it is true. (Page 183)
The Beginnings of Buddhism