Is calling to Allah an individual obligation, a collective obligation, or a recommended practice?

Question:
May Allah reward you with good, and may He do you good. Tell us about calling to Allah, and traveling for its sake to many places. In brief, is calling to Allah an individual obligation, a collective obligation, or a recommended practice? May Allah reward you with good.

Answer:
Good. Calling to Allah is obligatory upon the Muslims, obligatory as a collective obligation (fard kifayah). If those who are sufficient have fulfilled it, the obligation falls off the rest, and it remains for them as a recommended practice (sunnah) for whoever is able to do so—able in terms of knowledge, possessing the knowledge to convey it, calling people to Allah the Exalted with it, or making it clear to them. Also, one must be able to do so materially and physically. The best of deeds is calling to Allah, and it is the work of the Messengers (peace be upon them all), who all called to Allah, and it is the work of the Muslims. Allah said the Exalted: And calling has rulings and it has guidelines. Yes, yes. It is necessary for them to be present, the most important of which, as we mentioned, is knowledge. The person must be knowledgeable about what he is calling to, knowledgeable about what he is ordering, and knowledgeable about what he is forbidding. He must be able to remove the doubts (shubhah) with which the people of falsehood argue. This is the most important condition of calling, indeed this is based on knowledge. "Call to your Lord with wisdom," and wisdom means knowledge and placing things in their proper places. One who does not have knowledge cannot place things in their proper places. So he begins calling with the people closest to him, his family, his neighbors, and the people of his town, before other towns. If he has the capacity for travel and for what is around him, he also does what he is able of that, but the priority is to begin with the closest of the close.