Appears 6 times in the Quran.
3:134 ٱلَّذِينَ يُنفِقُونَ فِى ٱلسَّرَّآءِ وَٱلضَّرَّآءِ وَٱلْكَٰظِمِينَ ٱلْغَيْظَ وَٱلْعَافِينَ عَنِ ٱلنَّاسِ وَٱللَّهُ يُحِبُّ ٱلْمُحْسِنِينَ
Those who spend (benevolently) in ease as well as in straitness, and those who restrain (their) anger and pardon men; and Allah loves the doers of good (to others).
12:84 وَتَوَلَّىٰ عَنْهُمْ وَقَالَ يَٰٓأَسَفَىٰ عَلَىٰ يُوسُفَ وَٱبْيَضَّتْ عَيْنَاهُ مِنَ ٱلْحُزْنِ فَهُوَ كَظِيمٌ
And he turned away from them, and said: O my sorrow for Yusuf! and his eyes became white on account of the grief, and he was a repressor (of grief).
And when a daughter is announced to one of them his face becomes black and he is full of wrath.
40:18 وَأَنذِرْهُمْ يَوْمَ ٱلْءَازِفَةِ إِذِ ٱلْقُلُوبُ لَدَى ٱلْحَنَاجِرِ كَٰظِمِينَ مَا لِلظَّٰلِمِينَ مِنْ حَمِيمٍ وَلَا شَفِيعٍ يُطَاعُ
And warn them of the day that draws near, when hearts shall rise up to the throats, grieving inwardly; the unjust shall not have any compassionate friend nor any intercessor who should be obeyed.
43:17 وَإِذَا بُشِّرَ أَحَدُهُم بِمَا ضَرَبَ لِلرَّحْمَٰنِ مَثَلًا ظَلَّ وَجْهُهُۥ مُسْوَدًّا وَهُوَ كَظِيمٌ
And when one of them is given news of that of which he sets up as a likeness for the Beneficent Allah, his face becomes black and he is full of rage.
So wait patiently for the judgment of your Lord, and be not like the companion of the fish, when he cried while he was in distress.