What is better in the sight of Allah: to call to Islam or to study Islam for oneself?
Praise be to Allah, the Lord of the Worlds; and blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.
Knowledge is only a means to practise Sharia, nothing more. It is not an aim in itself. Everyone who learns something has to convey it to others as the Prophet said: "Convey from me to others even if it is a verse". Moreover calling to Islam needs sound knowledge and wisdom. Allah Says (interpretation of meaning): {Say (O Muhammad SAW): "This is my way; I invite unto Allâh (i.e. to the Oneness of Allâh - Islâmic Monotheism) with sure knowledge, I and whosoever follows me (also must invite others to Allâh i.e. to the Oneness of Allâh - Islâmic Monotheism) with sure knowledge. }[12:108]. One should not rely solely on himself in understanding the precepts of Islam, rather he should learn the texts through the explanations given by authentic scholars. Similarly, it is not proper to learn Islamic knowledge and fail to preach it to others as ignoring the job of preaching Islam is a great fault. Thus, Allah declared it a fault of the People of the Book. Allah Says (interpretation of meaning): {(And remember) when Allâh took a covenant from those who were given the Scripture (Jews and Christians) to make it (the news of the coming of Prophet Muhammadand the religious knowledge) known and clear to mankind, and not to hide it,….}[3:187].
To conclude, a person is obliged to learn what is compulsory for him, have a good AQIDA by correcting his faith and manners of worship, etc. Moreover, he is also commanded to convey to others the teachings of Islam and call them to the right path. There is no contradiction between these two acts. Allah knows best.
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