كتاب التوحيد
Read the English translation first, with the original Arabic directly underneath.
Narrated Jarir bin `Abdullah:
Allah's Messenger (ﷺ) said, "Allah will not be merciful to those who are not merciful to mankind."
لاَ يَرْحَمُ اللَّهُ مَنْ لاَ يَرْحَمُ النَّاسَ