Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrates that in the beginning, during prayer, we used to talk and greet each other, and would inform one another as needed. One day I came to the Prophet (peace and blessings be upon him) and greeted him with salam, but the Messenger of Allah (peace and blessings be upon him) did not reply. Various thoughts, both new and old, surrounded me. When the Prophet (peace and blessings be upon him) finished the prayer, he said, "Allah gives whatever new command He wishes. Thus, Allah has now revealed this new command that you should not talk during prayer."