he pbuh would call out the adhaan1 with or without repetition. he pbuh also pronounced the words of the iqaamah2 once or twice, except that he always repeated the words “qad qamat is-salaah” (prayer has begun) twice.
he pbuh ruled for his people that one who hears the adhaan should repeat the words after him, except for the words “hayya `alas-salaah" and "hayya `alal-falaah”, where one should say “la hawla wa la quwwata illa billaah." (there is no might and no power except through allah.”
he pbuh also said, “whoever hears the adhaan and then says: 'ash-hadu anla ilaaha ill-allah wa anna muhammadan rasulullah. raditu billaahi rabban, wa bil- islami deenan wa bi muhammadin rasulan' (i bear witness that there is no god but allah, and that muhammad is his messenger. i am pleased with allah as lord, islam as religion and muhammad as messenger) - whoever says that will have his sins forgiven."
he pbuh ruled that after repeating the words of the adhaan, one should invoke blessings upon the prophet pbuh, saying: “allaahumma rabba hadhihid-da`watit-taamma was-salaatil-qaa'imati, aati muhammadan al-waseelata wal-fadheelata, wab`ath-hu maqaaman mahmudan alladhi wa`adtah.'
(o allah, lord of this perfect call and present prayer, grant muhammad the waseelah (a position of intercession in paradise) and excellence and elevate him [on the day of judgment] to the praised position, which you have promised him.)
and he pbuh stated that supplication between the adhaan and iqaamah would never be refused [by allah].
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1 the call announcing that it is time for prayer.
2 a second call when the prayer is to begin.