By the Noble Scholar, Imaam ’Abdul-’Azeez Ibn Baaz (d.1420H)
From the necessary etiquette of the caller to Allaah. The noble Scholar, Ibn Baaz explains the importance of sincerity, mildness, knowledge and gentleness.
So a wrongdoer, who opposes the da’wah with evil and enmity and seeks to cause harm, is to be dealt with in a different manner. If possible such a person should be imprisoned, or something similar to that - depending upon the nature of his to the da’wah.
The etiquettes, manners and characteristics necessary for the du’aat (callers to Islaam) has been duly explained by Allaah - the Mighty and Majestic - in many aayaat and in many different places in the Noble Qur‘aan. And from those necessary etiquettes are:
FIRSTLY – SINCERITY:
So it is obligatory upon the daa’ee (caller) to have ikhlaas (sincerity and purity of intentions and actions) for Allaah - the Mighty and Majestic - neither desiring to show off, nor desiring reputation, nor desiring the praises and the accolades of the people. Rather, the daa’ee should only call to Allaah seeking the Face of Allaah, as He - the One free from all imperfections – says,
“Say: This is my path, I do call to upon knowledge.” 
And Allaah - the Mighty and Majestic – said,
“And who is better in speech than one who calls to Allaah.” 
Thus it is a must to have ikhlaas and to call only to Allaah - the Mighty and Majestic - and this is the most important etiquette and the greatest quality; that you seek from your da’wah (call) the Face of Allaah and the Home of the Hereafter.
SECONDLY – KNOWLEDGE:
To call the people to upon ’ilm (knowledge), and not ignorance,
“Say, This is my path, I do call to Allaah upon knowledge.”
So knowledge is an essential obligation in calling to Allaah. So beware of calling to Allaah based upon ignorance, and beware of speaking without due knowledge. Indeed, ignorance destroys, it does not build; and it causes corruption, not reformation and correction. So - O worshipper of Allaah - fear Allaah and beware of speaking about Allaah without due knowledge, and do not call to anything except after knowledge of it and having insight into what Allaah and His Messenger (sallallaahu ’alayhi wa sallam) have said. So it is upon the student of knowledge and the daa’ee to have knowledge of, and insight into that which they call to, knowing its proofs and evidences.
THIRDLY – MILDNESS AND GENTLENESS:
From the akhlaaq that it is necessary to have - O daa’ee - is to be mild and forbearing in your da’wah, and being gentle and patient in it, as were all the Messengers ’alayhimus-salaatu was-salaam. Beware of being hasty, harsh and strict in your da’wah, rather be patient, mild and gentle. In this regard, some of the proofs have already proceeded, such as the saying of Allaah - the Mighty and Majestic,
“Call to the way of your Lord with wisdom and beautiful admonition, and argue with them in ways that are best.”
And His - the Most Perfect’s – saying,
“And by the Mercy of Allaah you were able to deal gently with them. If you had been severe and harsh-hearted they would have broken away from about you.”
And His - the Most Majestic’s - saying, with regards to Moosaa and Haaroon - ’alayhimus-salaam,
“So speak to him mildly, perchance he may take admonition, or that he may fear Allaah.”
And the Prophet (sallallaahu ’alayhi wa sallam) said in the authentic hadeeth, “O Allaah! Whosoever is a guardian over any of the affairs concerning my Ummah and he is gentle with them, then be gentle with him. And whosoever is a guardian over any of the affairs concerning my Ummah and he is harsh with them, then be harsh with him.” 
So - O servant of Allaah - it is necessary upon you to be gentle in your da’wah and not to be harsh upon the people. Do not turn the people away from the Religion due to your harshness, ignorance, or other such behaviour. On the contrary, be mild, forbearing and patient; and be soft and pleasant in speech, so your words may have an effect upon the heart brother, or that it may have an effect upon the one you are addressing the call to. Then the people will better appreciate your call and invitation. So undue strictness causes people to become distant, not close; and it causes separation, not unity. Therefore, it is a must to be gentle, as the Messenger - ’alayhis-salaatu was-salaam – said, “Indeed gentleness does not enter into anything except that it beautifies it, is it removed from anything except that it disfigures it.”  And he - ’alayhis-salaatu was-salaam - also said, “Whoever is prevented from gentleness, is actually prevented from all good and excellence.” 
FOURTHLY – SETTING AN EXAMPLE:
From the necessary or rather obligatory - etiquettes and qualities that a daa’ee must possess is acting in accordance to what he is calling to, and being a righteous example of what is being called to. He should not call to do something and then not do it himself, nor call to leave something, whilst engaging in it himself. This is the condition of the losers - we seek Allaah’s refuge in this! It is those Believers who call to the truth, act upon what they call to the truth and hasten to righteousness and avoid the prohibited, these are the ones who will be successful and who will be rewarded. Allaah - the Most Majestic – says,
“O you who believe! Do you say that which you do not do. It is most hateful in the sight of Allaah that you say that which you do not do.”
Likewise, Allâh - the One free from all imperfections said, whilst condemning the Jews for ordering the people with righteousness whilst forgetting it themselves:
“Do you enjoin righteousness upon the people whilst you yourselves forget to practice it, and you recite the Book? Have you no sense?”
And it has been established from the Prophet (sallallaahu ’alayhi wa sallam) that he said, “A man will be brought on the Day of Judgement and he will be thrown into the Hellfire, so that his intestines will come out and he will go around like a donkey goes around the millstone. The people of Hellfire will gather around him and say, ‘O so and so! What happened to you? Did you not used to order us with good and prohibit us from evil?’ He will say, ‘I used to order you with good and not do it myself; and I used to prohibit you from evil and do it myself.” 
This will be the situation of the one who calls to Allaah, ordering the good and prohibiting the evil; whilst acting contrary to one’s saying, or saying things contrary to ones actions – we seek refuge in Allaah from this. Therefore, from the most important qualities and one greatest obligations upon the daa’ee is to act upon what he calls to and abstain from that which he prohibits. The daa’ee should have an excellent character and praiseworthy conduct, being patient and inviting to patience. The daa’ee should be sincere in his da’wah and strive in spreading goodness to the people and keeping them away falsehood. At the same time the daa’ee should supplicate for the guidance of others, saying, “O Allaah! Guide him, and grant him the ability to accept the truth.” So from the excellent manners of the daa’ee is supplicating, guiding and being patient with the harms that come with this da’wah.
When the Prophet (’alayhis-salaatu was-salaam was informed that the tribe of Daws had become disobedient he said, “O Allaah! Guide Daws and bring them.”  So the daa’ee should supplicate for guidance and ability to accept the truth for the one he is calling, and he should be patient and encourage patience in this. He should not despair, nor feel hopeless, nor say anything except good. He should not be harsh and strict, nor should he say a word which may cause aversion to the truth. However, if anyone commits aggression and oppression, then a different treatment is to be to such people, as Allaah - the Most Majestic - says:
“And do not argue with the people of the Book except in a good way, except those who do wrong.”
So a wrongdoer, who opposes the da’wah with evil and enmity and seeks to cause harm, is to be dealt with in a different manner. If possible such a person should be imprisoned, or something similar to that - depending upon the nature of his to the da’wah. However, as long as he causes no harm, then it upon you to be patient and self-evaluating and to debate with him in ways that are best. If any personal harm was caused by such a person, then such harm should be borne with patience - as did the Messengers and those who followed them in goodness and righteousness, patiently bear such harms.
I ask Allaah to grant us all the well-being and the ability to convey this da’wah in a wise manner, that He corrects our hearts and our actions, and that He grants to us the understanding of the Religion and firmness upon it making us of those who are guided and guiding others, righteous and teaching others righteousness. Indeed He is the Most Majestic, the Supreme, the Most Generous.”
 He is the exemplary Scholar, the zaahid mild and forbearing in nature, the faqeeh the muhaddith the Scholar of usool and Tawheed, Aboo ’Abdullaah ’Abdul-’Azeez Ibn ’Abdullaah Ibn Baaz. Born in the year 1330H (1911CE) in the city of Riyaad. He memorized the Qur‘aan before reaching the age of maturity and then went on to study under some of the major Scholars of the time. He excelled in the various branches of Islaamic sciences, even though he became permanently blind at a young age. He has devoted all of his life to the cause of Islaam and its people, authoring many books, teaching and serving the masses, whilst also aiding the spread of correct knowledge worldwide. May Allaah have mercy on him. This article has been taken from his booklet, ad-Da’wah Ilallaah wa Akhlaaqud-Du’aat (p. 37-43).
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 Soorah Fussilat [41:33]
 Soorah Yoosuf [12:108]
 Sooratun-Nahl [16:125]
 Soorah Aali-’Imraan [3:159]
 Soorah Taa Haa [20:44]
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 Sooratus-Saff [61:2-3]
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