Quran on Dawah: Al Imran: 110

You are the best of people raised up, for you call to all that is right and righteous and you forbid the evil, and you believe in Allah. ~Qur'an 3:110

There is an explanataion of this verse from Tafsir Ibn Kathir here.

Quran on Dawah: Surah Yusuf: 108

Say : "This is my way; I invite unto Allah with sure knowledge, I and whosoever follows me with sure knowledge" (Quran - 12:108)

There is a useful tafseer (exegesis or commentary) on this verses here

Quran on Dawah: Surah Aal-e-Imran: 104

"Let there arise out of you a group of people inviting to all that is good, enjoining what is right and forbidding what is wrong, and it is they who are succesful."

Quran on Dawah: An-Nahl: 125

“Invite to the Way of your Lord with wisdom and fair preaching, and argue with them in a way that is better. Truly, your Lord knows best who has gone astray from His Path, and He is the Best Aware of those who are guided.” (Quran, an-Nahl: 125)