In some Masjids (Mosques) when the Imam finishes the obligatory Salah (prayer), he supplicates to Allah raising his hands and people follow him in this regard.
Is there any proof which substantiates this act from the Qur'an and Sunnah? What is the ruling on those who claim that this is an obligatory act, could you kindly enlighten me?
We do not know any legal evidence on the permissibility of what you have mentioned in the question (Part No. 7; Page No. 105) It is reported from the Messenger (peace be upon him) that he said:
He who innovates things in our affairs for which there is no valid (reason) (commits sin) and these are to be rejected.
According to another narration:
He who did any act for which there is no sanction from our behalf, that is to be rejected.
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.