Sayyiduna Jabir bin Abdullah (may Allah be pleased with them both) narrates: Sayyiduna Ibn Umm Maktum (may Allah be pleased with him) came to the service of the Prophet (peace and blessings of Allah be upon him). He said: O Messenger of Allah (peace and blessings of Allah be upon him)! I am a blind man. My house is far away. He spoke to the Prophet (peace and blessings of Allah be upon him) about prayer, asking if he could be permitted to perform prayer at his home. The Prophet (peace and blessings of Allah be upon him) asked: Do you hear the call to prayer (adhan)? He replied: Yes. The Prophet (peace and blessings of Allah be upon him) said: Then join (the congregational prayer), even if you have to come crawling. (Imam Ibn Hibban, may Allah have mercy on him, says:) Sayyiduna Ibn Umm Maktum (may Allah be pleased with him) had requested the Prophet (peace and blessings of Allah be upon him) to grant him concession to not join the congregation. The statement of the Prophet (peace and blessings of Allah be upon him), "Join it even if you have to come crawling," is the greatest evidence that this command is obligatory, not merely recommended. Because whoever hears the call to prayer—if joining the congregation was not obligatory for him, the Prophet (peace and blessings of Allah be upon him) would have informed him that there is permission in this matter, since this answer was given in response to a similar question. So, it is impossible that something which is obligatory has no concession.