How the Adhan for Salat (Prayer) was started 

Hazrat Ibn Umar(ra) Narrated 

حَدَّثَنَا مَحْمُودُ بْنُ غَيْلاَنَ، قَالَ حَدَّثَنَا عَبْدُ الرَّزَّاقِ، قَالَ أَخْبَرَنَا ابْنُ جُرَيْجٍ، قَالَ أَخْبَرَنِي نَافِعٌ، أَنَّ ابْنَ عُمَرَ، كَانَ يَقُولُ كَانَ الْمُسْلِمُونَ حِينَ قَدِمُوا الْمَدِينَةَ يَجْتَمِعُونَ فَيَتَحَيَّنُونَ الصَّلاَةَ، لَيْسَ يُنَادَى لَهَا، فَتَكَلَّمُوا يَوْمًا فِي ذَلِكَ، فَقَالَ بَعْضُهُمْ اتَّخِذُوا نَاقُوسًا مِثْلَ نَاقُوسِ النَّصَارَى‏.‏ وَقَالَ بَعْضُهُمْ بَلْ بُوقًا مِثْلَ قَرْنِ الْيَهُودِ‏.‏ فَقَالَ عُمَرُ أَوَلاَ تَبْعَثُونَ رَجُلاً يُنَادِي بِالصَّلاَةِ‏.‏ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏ "‏ يَا بِلاَلُ قُمْ فَنَادِ بِالصَّلاَةِ ‏"‏‏.‏ 

When the Muslims arrived at Medina, they used to assemble for the prayer and used to guess the time for it. During those days, the practice of Adhan for the prayers had not been introduced yet. Once they discussed this problem regarding the call for prayer. Some people suggested the use of a bell like the Christians, others proposed a trumpet like the horn used by the Jews, but `Umar was the first to suggest that a man should call (the people) for the prayer; so Allah's Messenger (ﷺ) ordered Bilal to get up and pronounce the Adhan for prayers. (Sahih al-Bukhari 604) 

The Superiority of the Adhan 

Hazrat Abu Huraira(ra) Narrated 

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يُوسُفَ، قَالَ أَخْبَرَنَا مَالِكٌ، عَنْ أَبِي الزِّنَادِ، عَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ ‏ "‏ إِذَا نُودِيَ لِلصَّلاَةِ أَدْبَرَ الشَّيْطَانُ وَلَهُ ضُرَاطٌ حَتَّى لاَ يَسْمَعَ التَّأْذِينَ، فَإِذَا قَضَى النِّدَاءَ أَقْبَلَ، حَتَّى إِذَا ثُوِّبَ بِالصَّلاَةِ أَدْبَرَ، حَتَّى إِذَا قَضَى التَّثْوِيبَ أَقْبَلَ حَتَّى يَخْطُرَ بَيْنَ الْمَرْءِ وَنَفْسِهِ، يَقُولُ اذْكُرْ كَذَا، اذْكُرْ كَذَا‏.‏ لِمَا لَمْ يَكُنْ يَذْكُرُ، حَتَّى يَظَلَّ الرَّجُلُ لاَ يَدْرِي كَمْ صَلَّى ‏"‏‏.‏

Allah's Messenger (ﷺ) said, "When the Adhan is pronounced Satan takes to his heels and passes wind with noise during his flight in order not to hear the Adhan. When the Adhan is completed he comes back and again takes to his heels when the Iqama is pronounced and after its completion, he returns again till he whispers into the heart of the person (to divert his attention from his prayer) and makes him remember things which he does not recall to his mind before the prayer and that causes him to forget how much he has prayed."             (Sahih al-Bukhari 608)

«اَللهُ أَكْبَرُ، اَللهُ أَكْبَرُ ، اَللهُ أَكْبَرُ ، اَللهُ أَكْبَرُ »

Allaahu Akbar, Allaahu Akbar, Allaahu Akbar, Allaahu Akbar.

“Allah is the Most Great, Allah is the Most Great, Allah is the Most Great, Allah is the Most Great.”

«أَشْهَدُ أَنْ لَا إِلَهَ إِلَّا اللهُ، أَشْهَدُ أَنْ لَا إِلَهَ إِلَّا اللهُ »

Ash-hadu an laa ilaaha illaallaah, Ash-hadu an laa ilaaha illaallaah.

“I testify that none has the right to be worshiped except Allah, I testify that none has the right to be worshiped except Allah.”

«أَشْهَدُ أَنَّ مُحَمَّدًا رَسُولُ اللهِ، أَشْهَدُ أَنَّ مُحَمَّدًا رَّسُولُ اللهِ»

Ash-hadu anna Muhammadan rasoolullaah, Ash-hadu anna Muhammadan rasoolullaah.

“I testify that Muhammad is the Messenger of Allah, I testify that Muhammad is the Messenger of Allah.”

«حَيَّ عَلَى الصَّلَاةِ، حَيَّ عَلَى الصَّلَاةِ »

Hayya ‘alaas-salaah, Hayya ‘alaas-salaah.

“come to the prayer, come to the prayer.”

«حَيَّ عَلَى الْفَلَاحِ، حَيَّ عَلَى الْفَلَاحِ »

Hayya ‘alaal-falaah, Hayya ‘alaal-falaah.

“Come to the success, come to the success.”

Note: Only for Fajr prayer add the below sentence.

«اَلصَّلَاةُ خَيْرٌ مِنَ النَّوْمِ، اَلصَّلَاةُ خَيْرٌ مِنَ النَّوْمِ»

As-salaatu khayruminan-nawm, As-salaatu Khayruminan-nawm.

“The prayer is better than sleep, the prayer is better than sleep.”

« اَللهُ أَكْبَرُ ، اَللهُ أَكْبَرُ »

Allaahu Akbar, Allaahu Akbar.

‘Allah is the Most Great, Allah is the Most Great.’

« لَا إِلَهَ إِلَّا اللهُ »

Laa ilaaha illaallaah.

“None has the right to be worshiped except Allah.”