AN 5.159
PTS: A iii 184
Udayi Sutta: About Udayin
translated from the Pali by
Thanissaro Bhikkhu

I have heard that on one occasion the Blessed One was staying at Kosambi, in Ghosita's Park. Now at that time Ven. Udayin was sitting surrounded by a large assembly of householders, teaching the Dhamma. Ven. Ananda saw Ven. Udayin sitting surrounded by a large assembly of householders, teaching the Dhamma, and on seeing him went to the Blessed One. On arrival, he bowed down to the Blessed One and sat to one side. As he was sitting there he said to the Blessed One: "Ven. Udayin, lord, is sitting surrounded by a large assembly of householders, teaching the Dhamma."

"It's not easy to teach the Dhamma to others, Ananda. The Dhamma should be taught to others only when five qualities are established within the person teaching. Which five?

"[1] The Dhamma should be taught with the thought, 'I will speak step-by-step.'

"[2] The Dhamma should be taught with the thought, 'I will speak explaining the sequence [of cause & effect].'

"[3] The Dhamma should be taught with the thought, 'I will speak out of compassion.'

"[4] The Dhamma should be taught with the thought, 'I will speak not for the purpose of material reward.'

"[5] The Dhamma should be taught with the thought, 'I will speak without hurting myself or others.'[1]

"It's not easy to teach the Dhamma to others, Ananda. The Dhamma should be taught to others only when these five qualities are established within the person teaching."

Note

1.
According to the Commentary, "hurting oneself" means exalting oneself. "Hurting others" means putting other people down.

See also:Sn 4.8; AN 3.72; DN 16 (the Buddha's answer to Subhadda's question).