The obligation of Dawah has been made clear in the Qur'an. Allah (Glorified & Exalted Be HE) says in the Qur'an,
"Let there arise out of you a band of people inviting to all that is good,
enjoining what is right, and forbidding what is wrong:
they are the ones to attain felicity." (Al-Qur'an 3:104)
The Prophet (peace be upon him) said,"Convey from me, even (if it is) one verse." (Bukhari)
The Qur'an also tells us that not conveying the message amounts to disobedience to Allah (Glorified & Exalted Be HE),
"Those who conceal the clear (signs) We have sent down, and the guidance, after
We have made it clear for the people in the Book -on them shall be Allah's curse,
and the curse of those entitled to curse." (Al-Qur'an 2:159)
Conveying the message of Islam also means completing our own worship, the primary reason for which we were created. Dawah is one of the most noblest acts any Muslim can do and its rewards are immense. Allah (Glorified & Exalted Be HE) says in the Qur'an,
"Who is better in speech than one who calls (men) to Allah, works righteousness,
and says, "I am of those who bow in Islam"?" (Al-Qur'an 41:33)
The Prophet (peace be upon him) said, "Whoever guides (another) to a good deed will get a reward similar to the one who performs it." (Muslim).
He (peace be upon him) also said, "By Allah, if Allah were to guide one man through you it would be better for you than the best type of camels." (Bukhari and Muslim)
Da'wah is a duty upon us all