A verse and its Tafsir.
Allah the Exalted says:
“It was by the mercy of Allah that thou wast lenient with them (O Muhammad), for if thou hadst been stern and fierce of heart they would have dispersed from round about thee. So pardon them and ask forgiveness for them and consult with them upon the conduct of affairs. And when thou art resolved, then put thy trust in Allah. Lo! Allah loveth those who put their trust (in Him).” (3:159)
The term 'fazz' refers to one who is harsh.
The intended meaning here is
harshness in speech.
This is due to His statement thereafter:
"hard-hearted."
The meaning is:
Had you, O Muhammad, been foul-mouthed and hard-hearted toward the people,
they would have dispersed from you and abandoned you.
But Allah brought them together around you,
and [commanded you] to be gentle with them to soften their hearts.
Tafsir Ibn Kathir.