He wants to divorce his wife so that he will be free to focus on seeking knowledge
Question

I converted to Islam few years ago and was married at that time , my wife is still non Muslim but she never opposed Islam , now i have a daughter she is 2 years , but i have a desire to dedicate my life to Dawa for that i have to go study overseas for 5 -6 years what is a verdict on leaving a child with my wife who doesnt mind my daughter to learn quran or pray but she opposes Hijab strongly and stubbornly , and what is a verdict on of a divorce and leaving that child with her and go seek knowledge , please because i have asked many people that seem to have knowledge but none gave a clear answer
Praise be to Allah.We advise you not to abandon your wife and daughter and leave them as easy prey for any evildoer, or to let yourself be distracted from the obligation of taking care of them and looking after them by another duty. The first thing that the seeker of knowledge is obliged to do is to take care of his wife and family, whether they are Muslim or not, as Allah, may He be glorified and exalted, says (interpretation of the meaning): “And warn your tribe (O Muhammad) of near kindred” [ash-Shu ‘ara’ 26:214]. It was narrated that Abu Hurayrah (may Allah be pleased with him) said: They said: O Messenger of Allaah, whom should I treat kindly? He said, “Your mother.” He said: Then who? He said, “Your mother.” He said, Then who? He said, “Your mother.” He said, Then who? He said, “Your father.” He said: Then who? He said, “The next closest and the next closest.” Narrated by Ibn Maajah in as-Sunan (no. 3658), classed as saheeh by al-Albaani in Saheeh Ibn Maajah. 
Seeking knowledge has never formed a barrier between a man and his wife and children, but in the past it required making some sacrifices. But nowadays means of communication are widely available and people are better off, and the blessings of this world have become more accessible to them. Now it has become very easy for the seeker of knowledge to take his wife and children with him wherever he wants to travel to seek knowledge. If a person takes this decision, Allah, may He be glorified and exalted, will inevitably make things easy for him, if he seeks reward with Allah and intends that Allah should decree guidance, help and happiness for his family. By doing that, he is doing them the greatest possible favour that can be done in this world, which is guidance. In fact knowledge should only be sought in order to act upon it and call people to it, and priority should be given to one’s wife and children. Perhaps his reward will surpass by far the reward of the seeker of knowledge who is not sincere towards Allah and does not know how and where to seek that knowledge, so his knowledge will become a cause of troubles and misery for him – Allah forbid. 
If it is not possible for you to take your family with you, then you can follow a program for seeking knowledge on the Internet; there are many such programs, praise be to Allah. In fact nowadays many universities offer their certification to subscribers who follow the lectures on the Internet. You can also make use of summer courses that offer useful programs for a short period, for which it is acceptable for you to travel on your own; these are very effective courses and beneficial programs. 
Moreover, the things you are looking for of series of lessons and lectures, and commentaries on books, are recording and available on the Internet, and you can download them and study them yourself, or with a friend who is living in the same place. 
What matters in all these things is firm resolve, patience and perseverance in seeking and acquiring knowledge, pondering different aspects of it and learning its issues. If a person has this resolve, nothing can form a barrier between him and seeking knowledge, not even mountains of difficulties and obstacles. But the one who is weak in our opinion is the one who always says that he is not able to combine seeking knowledge and taking care of his family, or to combine seeking knowledge and earning a living. 
It was narrated that ‘Abdullah ibn ‘Amr (may Allah be pleased with him) said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “It is sufficient sin for a man to withhold provision from the one whose provision he controls.” Narrated by Muslim (996). 
If you read the biographies of some of the scholars who gave precedence to traveling in the pursuit of knowledge to taking care of their wives and children, that is because of what was dictated by circumstances in their time, which made it necessary to travel in order to acquire knowledge, which was basically narrations and hadeeths that it was not possible for the seeker of knowledge to acquire in his own city. But nowadays things are completely different; knowledge now is understanding and pondering, as well as studying and memorizing, and all of that can be achieved – as we have stated – by reading and studying, as well as making short trips to meet scholars, and by following their output via modern means of communication. Most of the scholars and seekers of knowledge whom we know have not resorted to what you are thinking of, namely divorcing your wife and abandoning your daughter; rather they have combined learning and helping their families, and by virtue of their eagerness and efforts they have become scholars who practise what they preach, praise be to Allah. 
And who knows, perhaps Allah may benefit your wife by means of you, and open her heart, and you may have the joy of seeing her become Muslim. 
Beware of falling into the most despised of that which is permissible, namely divorce, and abandoning your children who are in the greatest need of being with you, for the sake of something for which there are many alternative options, praise be to Allah. 
And Allah knows best.