Al-Adab Al-Mufrad, Book 20, Hadith 1 (In-Book) ⓘ
'Umar was heard to say, "Anyone who does not show mercy will not be shown mercy. Anyone who does not forgive will not be forgiven. Anyone who does not turn in repentance will not be turned to nor will he be protected or guarded."
حَدَّثَنَا حَفْصُ بْنُ عُمَرَ، قَالَ: حَدَّثَنَا شُعْبَةُ، عَنْ عَبْدِ الْمَلِكِ بْنِ عُمَيْرٍ، عَنْ قَبِيصَةَ بْنِ جَابِرٍ، عَنْ عُمَرَ قَالَ: لاَ يُرْحَمُ مَنْ لاَ يَرْحَمُ، وَلاَ يُغْفَرُ لِمَنْ لاَ يَغْفِرُ، وَلاَ يُتَابُ عَلَى مَنْ لاَ يَتُوبُ، وَلاَ يُوقَّ مَنْ لا يُتَوَقَّ.
also referenced under: Hadith 372 (Reference) & Book 20, Hadith 372 (English)