1. Udayi Thera - Also called Laludayi (and Pandita Udayi), to distinguish him from others. - He was the son of a brahmin of Kapilavatthu. He saw the power and majesty of the Buddha when the latter visited his kinsmen and, entering the Order, in due course became an arahant. When the Buddha preached the Nagopama Sutta (see A.iii.344f), on the occasion when Seta, King Pasenadis elephant, was publicly admired, Udayi was stirred to enthusiasm by thoughts of the Buddha and uttered sixteen verses, extolling the virtues of the Buddha, comparing him to a great and wondrous elephant. (Thag.vv.689-704; ThagA.ii.7f.; Udayis verses are repeated in the Anguttara (iii.346-7) but the Commentary (ii.669) attributes them to Kaludayi).
Once when Udayi was staying at Kamanda, in Todeyyas mango grove, he converted a pupil of a brahmin of the Verahaccani clan and, as a result, was invited by Verahaccani herself to her house. It was only on his third visit to Verahaccani that Udayi preached to her and she thereupon became a follower of the Faith (S.iv.121-4).
The Samyutta Nikaya (iv.166f.; another discussion with Ananda is mentioned in A.iv.426f) also records a conversation between Udayi and Ananda, when Udayi asks if it is possible to describe the consciousness, too, as being without the self. On another occasion Udayi has a discussion with Pancakanga on vedana (M.i.396ff; S.iv.223-4; the Commentary SA.iii.86 and MA.ii.629 here describes Udayi as Pandita). Ananda overhears their conversation and reports it to the Buddha, who says that Udayis explanation is true, though not accepted by Pancakanga.
Elsewhere (S.v.86ff) Udayi is mentioned as asking the Buddha to instruct him on the bojjhangas, and once, at Desaka (Setaka?) in the Sumbha country, he tells the Buddha how he cultivated the bojjhangas and thereby attained to final emancipation (S.v.89).
He is rebuked by the Buddha for his sarcastic remark to Ananda, that Ananda had failed to benefit by his close association with the Master. The Buddha assures him that Ananda will, in that very life, become an arahant (A.i.228).
Udayi was evidently a clever and attractive preacher, for he is mentioned as having addressed large crowds, a task demanding great powers, as the Buddha himself says when this news of Udayi is reported to him (A.iii.184).
According to Buddhaghosa (DA.iii.903), it is this same Udayi (Maha Udayi) who, having listened to the Sampasadaniya Sutta, is beside himself with joy at the contemplation of the wonderful qualities as set forth in that Sutta, and marvels that the Buddha does not go about proclaiming them. Buddhaghosa (MA.i.526) seems to identify him also with the Udayi to whom the Latukikopama Sutta (M.i.447ff) was preached.