The Command to say the phrases of the Adhan twice and the phrases of the iqamah once, except the phrase, "Prayer is about to begin," which is to be said twice

Sahih Muslim · Book 4 · Hadith 378 a

حَدَّثَنَا خَلَفُ بْنُ هِشَامٍ، حَدَّثَنَا حَمَّادُ بْنُ زَيْدٍ، ح وَحَدَّثَنَا يَحْيَى بْنُ يَحْيَى، أَخْبَرَنَا إِسْمَاعِيلُ ابْنُ عُلَيَّةَ، جَمِيعًا عَنْ خَالِدٍ الْحَذَّاءِ، عَنْ أَبِي قِلاَبَةَ، عَنْ أَنَسٍ، قَالَ أُمِرَ بِلاَلٌ أَنْ يَشْفَعَ، الأَذَانَ وَيُوتِرَ الإِقَامَةَ ‏.‏ زَادَ يَحْيَى فِي حَدِيثِهِ عَنِ ابْنِ عُلَيَّةَ فَحَدَّثْتُ بِهِ أَيُّوبَ…

Anas reported: Bilal was commanded (by the Messenger of Allah) to repeat (the phrases of) Adhan twice and once in Iqama. The narrator said: I made a mention of it before Ayyub who said: Except for saying: Qamat-is-Salat…

Sahih Muslim · Book 4 · Hadith 378 b

وَحَدَّثَنَا إِسْحَاقُ بْنُ إِبْرَاهِيمَ الْحَنْظَلِيُّ، أَخْبَرَنَا عَبْدُ الْوَهَّابِ الثَّقَفِيُّ، حَدَّثَنَا خَالِدٌ الْحَذَّاءُ، عَنْ أَبِي قِلاَبَةَ، عَنْ أَنَسِ بْنِ مَالِكٍ، قَالَ ذَكَرُوا أَنْ يُعْلِمُوا، وَقْتَ الصَّلاَةِ بِشَىْءٍ يَعْرِفُونَهُ فَذَكَرُوا أَنْ يُنَوِّرُوا نَارًا أَوْ يَضْرِبُوا نَاقُوسًا فَأُمِرَ بِلاَلٌ أَنْ يَشْفَعَ الأَذَانَ وَي…

Anas b. Malik reported: They (the Companions) discussed that they should know the timings of prayer by means of something recognized by all. Some of them said that fire should be lighted or a bell should be rung. But Bil…