"Thus you are appointed as the model community so that you may become witness against mankind and the Messenger is witness against you." [al-Qur’an 2 : 143]
It is through Allah (SWT)’s mercy that we are all Muslims and it is a Muslim’s obligation to convey the message of Islam according to his ability and knowledge.
"Convey from me, even if it is just one verse." [Sahih Bukhari]
As we live in a society which increasingly shows Islam in a negative light, it is a Muslim’s duty to separate the negative images people might associate with Islam, from the actual belief system.
"And do not debate with the People of the Book except with the best words, except for those who remain obstinately upon unbelief and would rather wage war." [al-Qur’an 20 : 46]
Due to Allah (SWT)’s mercy, no effort is wasted as there is also great reward for a Muslim who (through Allah (SWT)’s will) guides someone towards Islam.
"Whoever guides [another] to a good deed will get a reward similar to the one who performs it." [Sahih Muslim]
Da’wah is incumbent on all able Muslims and must be done in compliance with the methodology already established by the last Prophet of Islam, Muhammad, peace and blessing be upon him.
"Invite (all) to the Way of thy Lord with wisdom and beautiful preaching; and argue with
them in ways that are best and most gracious." [al-Qur’an 16 : 125 ]