He also said

When I asked God’s Messenger to teach me the sunna relating to the adhan he wiped the forepart of his head and said: You must say, “God is most great. God is most great. God is most great. God is most great,” raising your voice while saying these words. Then you must say, “I testify that there is no god but God. I testify that there is no god but God. I testify that Muhammad is God’s Messenger. I testify that Muhammad is God’s Messenger,” lowering your voice while saying these words. Then you must raise your voice in making the testimony, “I testify that there is no god but God. I testify that there is no god but God. I testify that Muhammad is God’s Messenger. I testify that Muhammad is God’s Messenger. Come to prayer. Come to prayer. Come to salvation. Come to salvation”; and if it is the Morning Prayer you must say, “Prayer is better than sleep. Prayer is better than sleep. God’s is most great. God is most great. There is no god but God.” Abu Dawud transmitted it.