Which one is better in the sight of Allah (higher reward in the day of judgement): a man who is working a full-time secular job and teaches Islam on a part-time basis or a man who is learning and teaching Islam on a full-time basis as this is his job. Which of these 2 is better?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

It is obligatory on every Muslim to aquire the necessary Islamic knowledge which helps him correct his ‘Aqeedah belief, worship Allah in the way He prescribed, and know the lawful and unlawful in his daily life. This is a common obligation on every Muslim; so every Muslim has to attain this degree of knowledge. After acquiring this amount of knowledge, it is obvious that the person who does much good deeds is better than the one who does less. Keep in mind that there the priority is not defined simply on the basis of gaining vast knowledge, higher degrees or good qualifications. Rather, the priority depends on practicing Islam according to one's knowledge and spending as much effort as possible to preach Islam and support Muslims. Indeed, the one who teaches Islam on a part-time basis and the one who teaches it on a full-time basis both are performing a good job. The comparison between them would be on the basis of each one's efforts, sacrifice and hard work done for Allah's Sake. In fact, we have noticed that the person who works in his field in the morning and then devotes himself to teaching Islam and making Da’wah in the evening is blessed in his work and his achievements are greater than the one who works for Islam on a full-time basis. However, one who works in a secular field serving Muslims or making people aware of Islam by his manners and good character also performs an admirable work. We should not consider his work less important. The most important matter is that one should be sincere in his work and acts according to Sunnah. When these two basic conditions are met, the act becomes precious and Allah accepts it, Allah willing.

Allah knows best.