Sayyar bin Ma’rur says that once I heard Sayyiduna Umar (may Allah be pleased with him) saying during a sermon that the construction of this mosque was carried out by the Prophet (peace and blessings be upon him) together with the Muhajirun and Ansar. If the crowd becomes too large (instead of blaming the lack of space in the mosque), perform prostration on your brother’s back. Similarly, once Sayyiduna Umar (may Allah be pleased with him) saw some people praying on the road and said: Perform prayer in the mosque.