Abdullah ibn Amr reported: The Messenger of Allah, peace and blessings be upon him, was upon the pulpit and he said:

ارْحَمُوا تُرْحَمُوا وَاغْفِرُوا يَغْفِرْ اللَّهُ لَكُمْ

Be merciful to others and you will receive mercy. Forgive others and Allah will forgive you.

Source: Musnad Ahmad