Among the verses revealed on leniency, Allah (Exalted be He) says, And by the Mercy of Allâh, you dealt with them gently. And had you been severe and harshhearted, they would have broken away from about you; so pass over (their faults), and ask (Allâh's) Forgiveness for them; and consult them in the affairs.
Allah (Exalted be He) says regarding the story of Musa (Moses) and Harun when He sent them to Pharaoh, "And speak to him mildly, perhaps he may accept admonition or fear (Allâh)."
Allah (Exalted be He) also says, Invite (mankind, O Muhammad ﺻﻠﻰ ﺍﷲ ﻋﻠﻴﻪ ﻭ ﺳﻠﻢ) to the Way of your Lord (i.e. Islâm) with wisdom (i.e. with the Divine Revelation and the Qur'ân) and fair preaching, and argue with them in a way that is better.