Hadith: The Messenger of Allah (ﷺ) used to start the prayer with Takbīr and then recite: {All praise be to Allah, the Lord of the worlds}

عَنْ عَائِشَةَ أُمِّ المُؤْمِنين رَضيَ اللهُ عنها قَالَتْ:
كَانَ رَسُولُ اللهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ يَسْتَفْتِحُ الصَّلَاةَ بِالتَّكْبِيرِ، وَالقِرَاءَةِ، بِـ الحَمْدُ لِلَّهِ رَبِّ العَالَمِينَ، وَكَانَ إِذَا رَكَعَ لَمْ يُشْخِصْ رَأْسَهُ وَلَمْ يُصَوِّبْهُ، وَلَكِنْ بَيْنَ ذَلِكَ، وَكَانَ إِذَا رَفَعَ رَأْسَهُ مِنَ الرُّكُوعِ لَمْ يَسْجُدْ حَتَّى يَسْتَوِيَ قَائِمًا، وَكَانَ إِذَا رَفَعَ رَأْسَهُ مِنَ السَّجْدَةِ لَمْ يَسْجُدْ حَتَّى يَسْتَوِيَ جَالِسًا، وَكَانَ يَقُولُ فِي كُلِّ رَكْعَتَيْنِ التَّحِيَّةَ، وَكَانَ يَفْرِشُ رِجْلَهُ اليُسْرَى وَيَنْصِبُ رِجْلَهُ اليُمْنَى، وَكَانَ يَنْهَى عَنْ عُقْبَةِ الشَّيْطَانِ، وَيَنْهَى أَنْ يَفْتَرِشَ الرَّجُلُ ذِرَاعَيْهِ افْتِرَاشَ السَّبُعِ، وَكَانَ يَخْتِمُ الصَّلَاةَ بِالتَّسْلِيمِ.
[صحيح] - [رواه مسلم] - [صحيح مسلم: 498]

‘Ā’ishah, the Mother of the Believers (may Allah be pleased with her), reported:
The Messenger of Allah (ﷺ) used to start the prayer with Takbīr and then recite: {All praise be to Allah, the Lord of the worlds}. When he bowed, he neither raised his head nor lowered it, but kept it level. When he raised his head from bowing, he would not prostrate until he had fully stood upright. When he raised his head from prostration, he would not prostrate (again) until he had sat upright. After each two Rak‘ahs (units of prayer), he would recite the Tahiyyah (greeting). He would spread his left foot out and erect his right foot. He would forbid sitting in the manner of the devil and resting the forearms on the ground, as a wild beast (i.e., lion) does. He would conclude the prayer with Taslīm (a salutation of peace that ends the prayer).
[Authentic hadith] - [Narrated by Muslim] - [Sahih Muslim - 498]

Explanation

The Mother of the Believers ‘Ā’ishah (may Allah be pleased with her) mentioned the prayer of the Prophet (ﷺ) that he would begin his prayer with the opening Takbīr, saying: "Allāhu Akbar (Allah is the Greatest)," and he would begin the recitation with Surat al-Fātihah: {All praise be to Allah, the Lord of the worlds...}. And when he bowed after standing, he would neither raise nor lower his head while bowing, but kept it level and straight. When he raised his head from bowing, he would stand upright before going into prostration. And when he raised his head from the first prostration, he would not go into the second until he was completely settled in the sitting position. He would sit after every two Rak‘ahs for the Tashahhud (sitting of testimony) and say: "At-Tahiyyātu lillāhi was-salawātu wat-tayyibāt..." (Greetings, prayers, and good things are due to Allah...). When sitting between the two prostrations or for the Tashahhud, he would spread his left foot and sit upon it, and erect his right foot. He forbade a person praying from sitting in prayer like the sitting of the devil—that is, by spreading his feet flat on the ground and sitting on his heels, or by placing his buttocks on the ground while erecting his legs and resting his hands on the ground like a dog does. He also forbade spreading one's forearms flat on the ground during prostration, as wild beasts do. He would conclude his prayer with Taslīm: "As-salāmu ‘alaykum wa rahmatullāh (Peace and mercy of Allah be upon you)," once to the right and once to the left.

Benefits from the Hadith

1. Highlighting some aspects of the Prophet's manner of performing prayer.
2. The obligation of the Opening Takbīr, which prohibits any speech or action inconsistent with what is to be said and done in prayer.Nothing else can serve as a substitute for it as the means of commencing the prayer.”
3. The obligation of reciting Al-Fātihah.
4. Rukū‘ (bowing) is obligatory, and the best manner of performing it is with the back being level, neither raised nor lowered.
5. Rising from bowing is obligatory, as is standing upright and straight after it.
6. Sujūd (prostration) is obligatory, as is rising from it and sitting upright in balance afterward.
7. It is legitimate for the person praying to spread his left leg and keep his right foot erect while sitting during prayer. As for the final Tashahhud in prayers that have two Tashahhuds, such as Maghrib and ‘Ishā’, the prescribed posture is Tawarruk (sitting with the left thigh on the ground and the right foot erect), as mentioned in other Hadīths.
8. The prohibition against imitating the sitting posture of the devil, which is to sit on one's heels while spreading the feet flat on the ground, or to place both feet upright and sit between them on the ground.
9. The prohibition against resembling a wild beast in its manner of lying down—that is, when the person praying spreads his forearms flat on the ground during prostration—for this posture reflects laziness and weakness.
10. The prohibition against imitating the devil or animals in their actions.
11. The obligation to conclude the prayer with Taslīm, which is a supplication for safety and well-being from all evils and shortcomings for oneself, the worshippers present, and the absent righteous believers.
12. The obligation of tranquility during prayer.