On the authority of Ibn ‘Abbas (may Allaah be pleased with them both).
He (the Prophet – may Allah bless him and grant him peace) said:
“Teach (others), and make things easy (for people) and do not make things difficult, and if one of you becomes angry then let him remain silent.”
Reference: Saheeh al-Jaami as-Saghir wa Ziyaadah, Hadeeth Number 4027.
Shaikh al-Albaanee (may Allaah have upon him) said the Hadeeth is Saheeh.