What is the ruling of end of (Thashood) every prayers we say Assalamu Alaikum (Left and Right sides) to whom we say and if any one say Salaam since it is must to reply. What is the ruling of we say Salaam?

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.

Saying "Assalaamu Alaykum" at the end of the prayer is a pillar of the prayer according to the majority of the scholars   without which the prayer is void. Some scholars are of the view that the best form of Tasleem is saying: "Assalaamu Alaykum Wa Rahmatu Allaah".

As regards the ones addressed by this Salaam, they are the Angels, the believing Jinns and the Muslims if the sayer is the Imam. When the Muslims who are praying with the Imam say "Assalamu Alaykum", it is a reply to the Imaam's Salaam.

An-Nawawi said: "It is desirable for the Imaam to intend by the first Tasleem on his right to say Salaam to the angels, the Muslim Jinns and the Muslim people on his right, and to intend, by his second Tasleem, to say Salaam on the Angels, the Muslim Jinns and the Muslims on his left. The person praying behind the Imaam should also have the same intention."

If the person praying behind is at the right hand of the Imaam, he should intend with the second Tasleem to reply to the Salaam of the Imaam. And if he is on his lef side, he should intend this with his first Tasleem, and if he is right behind the Imaam, then he may intend to say Salaam to the Imaam with any Tasleem.

As for the person praying alone, he should intend by his Tasleem, to say Salaam to the Angels [and believing Jinns] on both his right and his left hand sides.

Finally, it should be mentioned that the person who is outside the prayer and who hears a praying person saying Salaam, is not asked to reply to him as this Salaam is not addressed to him.

Allaah Knows best.