Sayyiduna Anas bin Malik (may Allah be pleased with him) narrates that in the blessed era of the Messenger of Allah (peace and blessings be upon him), when the time for prayer would arrive, a man would walk along the road calling out, "Prayer, prayer, prayer." This became burdensome for the people, so they said, "O Messenger of Allah, if we start ringing a bell (it would be better)." The Prophet (peace and blessings be upon him) said, "That is the practice of the Christians." They said, "If we start blowing a horn (that would also be fine)." The Prophet (peace and blessings be upon him) said, "That is the practice of the Jews." It is said that Sayyiduna Bilal (may Allah be pleased with him) was commanded to say the words of the adhan twice and the words of the takbir once.