{Invite (mankind, O Muhammad ) to the Way of your Lord (i.e. Islam) with wisdom (i.e. with the Divine Inspiration and the Qur’an) 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.}
(Holy Quran-16:125)

{And who is better in speech than he who [says: “My Lord is Allah (believes in His Oneness),” and then stands straight (acts upon His Order), and] invites (men) to Allah’s (Islamic Monotheism), and does righteous deeds, and says: “I am one of the Muslims.”} (Holy Quran-41:33)

The prophet (peace and blessings of Allah be upon him) said: “By Allah, if Allah guides one person by you, it is better for you than the best types of camels.” [al-Bukhaaree, Muslim]

The prophet (peace and blessings of Allah be upon him) also said, “Whoever calls to guidance will have a reward similar to the reward of the one who follows him, without the reward of either of them being lessened at all.”
[Muslim, Ahmad, Aboo Daawood, an-Nasaa’ee, at-Tirmidhee, Ibn Maajah]