Allah Ta’ala says in the Qur’an:
قل هذه سبيلي أدعو إلى الله على بصيرة أنا ومن اتبعني وسبحان الله وما أنا من المشركين
To the meaning of: “Say, “This is my way; I invite to Allah with insight, I and those who follow me. And exalted is Allah ; and I am not of those who associate others with Him.”
And He Subhanaahu wa ta’ala also said:
لقد من الله على المؤمنين إذ بعث فيهم رسولا من أنفسهم يتلو عليهم آياته ويزكيهم ويعلمهم الكتاب والحكمة وإن كانوا من قبل لفي ضلال مبين
To the meaning of: “Certainly did Allah confer [great] favor upon the believers when He sent among them a Messenger from themselves, reciting to them His verses and purifying them and teaching them the Book and wisdom, although they had been before in manifest error.” 
And He azza wa jal said:
الذين يستمعون القول فيتبعون أحسنه أولئك الذين هداهم الله وأولئك هم أولو الألباب
To the meaning of: “Who listen to speech and follow the best of it. Those are the ones Allah has guided, and those are people of understanding.”
The ayat above explain that the way best way to invite others to Islam is through sure knowledge and wisdom. The caller or da’ee should always thrive to invite others with what knowledge he or she has “be it even a single ayat” as Rasul Allah salAllahu alaihi wa sallam had famously stated in a saheeh hadith.
It therefore becomes obligatory on each muslim to invite others to the deen of al-Islam with knowledge and wisdom. The more knowledge a da’ee has the better and stronger the arguments for Islam become, which also makes the da’ee more confident when inviting as the proofs for become overwhelming, thus making a more successful daee.
We have great examples of our dear Prophet Muhammed salAllahu alaihi wa sallam which illustrate the different ways of calling people to Islam, be it with only gestures, hard or soft words depending on the situation and person/persons involved and always with wisdom.
It has been narrated from Nabi salAllahu alaihi wa sallam about acquiring knowledge:
“God, His angels and all those in Heavens and on Earth, even ants in their hills and fish in the water, call down blessings on those who instruct others in beneficial knowledge.”
“Acquire knowledge and impart it to the people.”
If anyone travels on a road in search of knowledge, God will cause him to travel on one of the roads of Paradise. The angels will lower their wings in their great pleasure with one who seeks knowledge. The inhabitants of the heavens and the Earth and (even) the fish in the deep waters will ask forgiveness for the learned man. The superiority of the learned over the devout is like that of the moon, on the night when it is full, over the rest of the stars. The learned are the heirs of the Prophets, and the Prophets leave (no monetary inheritance), they leave only knowledge, and he who takes it takes an abundant portion.
The quoted hadeeth above show us the importanance of knowledge as ordered by Rasul Allah salAllahu alaihi wa sallam.
Knowledge is a necessity for those seeking Allaah’s Pleasure and success in the Hereafter. For such a person, the need for knowledge is greater than his need for food or drink. The Prophet salAllahu alaihi wa sallam said, “He who sets foot on a path in the quest of knowledge, Allaah will facilitate for him the path to Paradise.”
Ibn Rajab Al-Hanbalee said on the explanation of this Hadeeth, “Knowledge leads to Allaah through the shortest and easiest paths. So, whoever sets foot on Allaah’s path and does not swerve from it will definitely reach Allaah and Paradise through the shortest and easiest paths.”
For those who wish to be among the pious, knowledge is the road to piety. One of the Salaf said, “How could one be pious if he does not know what things to avoid?”
Ma’roof Al-Karkhi said, “If you do not know how to fear Allaah, You will certainly eat riba (usury).”
Ibn Rajab Al-Hanbalee said, “The essence of piety is that the servant should know first what to avoid and then avoids it.”
The knowledge we need has been concentrated by the scholars into two areas: knowledge of Allaah, and knowledge of His instructions. The first type concerns knowledge of Allaah’s Names and Attributes. Such knowledge provides the Muslim with fear, humility, obedience and submission to Allaah. It is the most honourable and highest type of knowledge because its subject is Allaah (SWT). Many of our pious predecessors said, “Knowledge is not a matter of many narrations, but it is a matter of fearing Allaah“. Others said, “Sufficient is knowledge which brings about fear of Allaah.”
Imam Ahmad bin Hanbal said, “The knowledge a person must have is that which he has to acquire in order to perform his Salah and establish his faith.”
All members of the Jama’ah are required to possess sufficient ‘knowledge of Allaah’ to enable them to obey Him, undertake His commands and shun disobeying Him. They should compete with one another to acquire this knowledge, for those who know the most are the closest to Allaah. Then they should acquire the knowledge whereby their ‘Aqeedah, as well as their worship and dealings with others, is correct and acceptable to Him. This is an obligation of individual responsibility, each in accordance with what he requires for his faith and worldly affairs. This knowledge should then be further used to convey the message to the ones most in need of it.
It must also be notes that, he salAllahu alaihi wa sallam made special du’a for those who learn his sayings and transmit them to others: Zayd Ibn Thabit narrated that the Prophet said, “May Allah brighten the face of the person who hears what I say and retains it, then conveys it to others: for sometimes one who hears from another remembers it better than the original hearer himself.” (Related by Ahmad and Tirmithi)
He assured all those who disseminate his knowledge that they will get the same reward of any Muslim who acts upon that knowledge: Abu Hurayrah relates that the Prophet salAllahu alaihi wa sallam said, “He who calls another to guidance will have a reward equal; to the reward of him who follows him without diminishing the reward of either of them.” (Related by Muslim)
He showed to us the noble status of the learned people of His Ummah: Abu Umamah relates that the Prophet salAllahu alaihi wa sallam said, “A learned one is as much above an (ordinary) worshiper as I am above the least of you; and he added: Allah, His angels and all those in the heavens and in the earth, even the ants in their holes and the fish in the water, call down blessings on those who instruct people in beneficent knowledge.” (Related by Tirmidhi)
Better still, he declared that the ‘Ulama’ (those who have Islamic knowledge) are his heirs: Abu Darda’ said that he heard the Prophet salAllahu alaihi wa sallam saying, “The ‘Ulama’ are heirs of the Prophets, and the Prophets do not leave an inheritance of Dirhams and Dinars but (they left) only knowledge. He who acquires knowledge acquires a vast portion.” (Related by Abu Dawud and Tirmidhi)
A note must be made and it must be stated that those with knowledge who choose not to use it to convey the message to the disbeleivers are surely at a loss as Umar bin Al-Khattab radiAllahu anhu rightly said, “What I fear most for you is a hypocrite with a knowledgeable tongue.”
In conclusion, it becomes all so clear that when a servant of Allah is granted knowledge, he appreciates Allah’s creation more, and becomes more acquainted with Allah’s attributes and qualities, thus becoming more confident and assured when calling others to Islam. Consequently, he wholeheartedly witnesses that his Creator is the only one worthy of worship, and then submits to Him Ta’ala humbly. This, in return, generates in his heart a fear, which is akin to a full appreciation and love of His Lord. Allah subhaanaahu has witnessed in favour of His learned servants these qualities, full appreciation of His Oneness and fear of Him.
سبحانك اللهم وبحمدك، أشهد أن لا إله إلا أنت، أستغفرك وأتوب إليك
والله تعالى أعلم
وصلى اللهم وسلم وبارك على نبينا محمد وعلى آله وصحبه والتابعين
أخوك أبو ناصر