"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.'

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