One of the two teachers to whom Gotama, after his renunciation, first attached himself, the other being Uddaka Rāmaputta. In the Ariyaparivesāna Sutta MN.i.163–165; also M.i.240ff. MN.ii.94ff. MN.ii.212ff. the Buddha describes his visit to Āḷāra. Gotama quickly mastered his doctrine and was able to repeat it by heart; but feeling sure that Āḷāra not only knew the doctrine but had realised it, he approached him and questioned him about it. Āḷāra then proclaimed the Ākiñcaññāyatana, and Gotama, putting forth energy and concentration greater than Āḷāra’s, made himself master of that state. Āḷāra recognised his pupil’s eminence and treated him as an equal, but Gotama, not having succeeded in his quest, took leave of Āḷāra to go elsewhere. When, after having practised austerities for six years, the Buddha attained Enlightenment and granted Sahampati’s request to preach the doctrine, it was of Āḷāra he thought first as being the fittest to hear the teaching. But Āḷāra had died seven days earlier. Vin.i.7

The Mahā Parinibbāna Sutta DN.ii.130 mentions a Mallian, Pukkusa, who says he had been Āḷāra’s disciple, but who, when he hears the Buddha’s sermon, confesses faith in the Buddha. Pukkusa describes Āḷāra to the Buddha as one who practised great concentration. Once Āḷāra was sitting in the open air and neither saw nor heard five hundred passing carts though he was awake and conscious.