Hawzah News Agency – The commander of the faithful, Imam Ali peace be upon him says:

إيّاكُم والمِراءَ والخُصومَةَ؛ فإنّهُما يُمرِضانِ القُلوبَ علَى الإخوانِ ويَنبُتُ علَيهِما النِّفاقُ.

'Beware of disputing and quarrelling, for they sicken the heart against one's brethren and give rise to hypocrisy against them.'

Source: al-Kafi, v. 2, p. 300, no. 1