How to Invite People to Islam: Quranic and Prophetic Guidance

There are different ways to convince people to the right cause from the perspective of the Quran and Sunnah. Some of them are:

Appealing to the heart, intuition, and experience
The Quran and Sunnah teach that human beings have a natural instinct (fiṭrat Allāh) to recognize their Creator and seek the truth. This instinct can be awakened by reminding people of the signs of God in themselves and in the universe, and by appealing to their emotions, feelings, and conscience. 

فَأَقِمْ وَجْهَكَ لِلدِّينِ حَنِيفًا ۚ فِطْرَتَ ٱللَّهِ ٱلَّتِى فَطَرَ ٱلنَّاسَ عَلَيْهَا ۚ لَا تَبْدِيلَ لِخَلْقِ ٱللَّهِ ۚ ذَٰلِكَ ٱلدِّينُ ٱلْقَيِّمُ وَلَٰكِنَّ أَكْثَرَ ٱلنَّاسِ لَا يَعْلَمُونَ

So direct your face toward the religion, inclining to truth. [Adhere to] the fitrah of Allah upon which He has created [all] people. No change should there be in the creation of Allah. That is the correct religion, but most of the people do not know. [Al Quran 30.30]

Appealing to the mind, logic, and reason
The Quran and Sunnah also teach that human beings have been endowed with intellect (‘aql) and free will (ikhtiyār) to discern between right and wrong. This intellect can be stimulated by presenting rational arguments, evidences, and proofs for the existence of God, the prophethood of Muhammad ﷺ, and the authenticity of the Quran. 

لَآ إِكْرَاهَ فِى ٱلدِّينِ ۖ قَد تَّبَيَّنَ ٱلرُّشْدُ مِنَ ٱلْغَىِّ ۚ فَمَن يَكْفُرْ بِٱلطَّٰغُوتِ وَيُؤْمِنۢ بِٱللَّهِ فَقَدِ ٱسْتَمْسَكَ بِٱلْعُرْوَةِ ٱلْوُثْقَىٰ لَا ٱنفِصَامَ لَهَا ۗ وَٱللَّهُ سَمِيعٌ عَلِيمٌ

There shall be no compulsion in [acceptance of] the religion. The right course has become clear from the wrong. So whoever disbelieves in Taghut and believes in Allah has grasped the most trustworthy handhold with no break in it. And Allah is Hearing and Knowing. [Al Quran 2.256]

Being good to others
The Quran and Sunnah instruct Muslims to be kind, merciful, forgiving, generous, just, and respectful to others, especially to their parents, relatives, neighbors, orphans, travelers, and those in need. By being good to others, Muslims can show the beauty and morality of Islam through their actions and character. The Prophet ﷺ said: 

“Whenever kindness becomes part of something, it beautifies it. Whenever it is taken from something, it leaves it defective.” (Muslim 2594)

إِنَّ الرِّفْقَ لاَ يَكُونُ فِي شَىْءٍ إِلاَّ زَانَهُ وَلاَ يُنْزَعُ مِنْ شَىْءٍ إِلاَّ شَانَهُ

Speaking mildly and politely
The Quran and Sunnah advise Muslims to speak to people with gentle speech, good words, wisdom, and fair preaching. By speaking mildly and politely, Muslims can avoid offending or hurting others, and can invite them to the right cause with compassion and grace. The Prophet ﷺ said:

 “The believer does not insult others, curse others, speak obscenely or speak rudely.” (Sunan al-Tirmidhi)

لَيْسَ الْمُؤْمِنُ بِالطَّعَّانِ وَلاَ اللَّعَّانِ وَلاَ الْفَاحِشِ وَلاَ الْبَذِيءِ 

[Jami` at-Tirmidhi 1977]