The Ruling on Calling Non-Muslims to Islam

First question:
Is calling non-Muslims to enter Islam obligatory upon Muslims? And how can this be implemented?

Answer:
Yes, calling non-Muslims to Allah is obligatory [Al-Hajj:67]. This is for non-Muslims. Muslims have already entered Islam, but they need more good. As for the disbeliever, he is the most in need of this, and the greatest in need of being called, and of being shown the truth in the language he knows, or by translation if you do not know his language.
So the polytheists, from among the worshippers of idols, the Christians, and others, even the Jews, if it is possible to call them to Allah, they are to be called to Allah. Even the communists, if it is possible through wisdom and kind words, this is required. So all the people of the earth, all the disbelievers, it is obligatory that they be called to Allah, if the caller to Allah is able to do so and has the capacity for it. The call to Allah becomes obligatory for these people... just as a Muslim is called to Allah regarding what he has neglected or what he has been lazy about.