Silsilat al-Ahadith al-Sahihah

It is narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: “Just as there are signs and marks on a road, there are also some signs and marks of Islam. Some of them are: to have faith in Allah and not to associate anyone with Him, to establish prayer, to pay zakat, to fast in Ramadan, to perform Hajj to the House of Allah, to enjoin good, to forbid evil, to greet one’s family when entering the house, and to greet people when passing by them. Whoever falls short in any of these matters, it means that he has abandoned a part of Islam, and whoever abandons all of these things, he has turned his back on Islam (or has cast Islam behind him).”