Why is it that the Mahdi is called "alayhi as-salaam" even though he is not a prophet? Abu Bakr, 'Umar, 'Uthmaan and 'Ali are not called "peace be upon them" but Al-Mahdi is said as I hear many times "peace be upon him"?Why is it only the Mahdi?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

Some scholars are of the view that the expression 'Alayhi As-Salaam is not said to other than the Prophets. Imaam Abu Muhammad Al-Juwayni said: 'It cannot be designated for other than the Prophets. So we do not say 'Ali Alayhi As-Salaam and it is not said for anyone whether alive or dead. As regards a living person, he is addressed by: ''Salaamun 'Alayka'', ''Salaamun 'Alaykum'' or ''As-Salaam 'Alayka.'

Our righteous predecessors did not use the phrase "As-Salat" or "As-Salaam" for other than the Prophets. Similarly the word 'Azzawajal (All-Mighty) is used only for Allaah. So we do not say Muhammad 'Azzawajal even though he was well-beloved and dignified, and we do not say 'Alayhi As-Salaam for other than Prophets. Saying 'Alayhi As-Salaam to other than the Prophets is a slogan of innovators. We are forbidden to say their slogan, so we do not say Al-Mahdi 'Alayhi As-Salaam nor do we say Abu-Bakr 'Alayhi As-Salaam, may Allaah be pleased with all of them.

Allaah knows best.