Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) narrates that in the beginning, we used to talk and greet each other during prayer, and would inform each other as needed. One day I came to the Prophet (peace and blessings of Allah be upon him) and greeted him, but he did not reply. Various thoughts, both new and old, surrounded me. When the Prophet (peace and blessings of Allah 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."