The Messenger of Allah ﷺ used to pray Dhuhr in the intense midday heat, and there was no prayer harder on the companions of the Messenger of Allah ﷺ than that one. Then this was revealed, "Guard strictly the prayers, and the middle prayer" [Baqarah 2:238].He said, "There are two prayers before it and two prayers after it."
كان رسول الله ﷺ يصلى الظهر بالهاجرة ولم يكن يصلي صلاة أشد على أصحاب رسول الله ﷺ منها، فنزلت: {حفظوا على الصلوات والصلوة الوسطى} وقال: إن قبلها صلاتين، وبعدها صلاتين.
Abu Dawud reported it (411), saying, Muhammad bin Muthanna narrated to us, Muhammad bin Jafar narrated to me, Shuba narrated to us, Amr bin Abu Hakeem narrated to me, he said, I heard Zubarqan narrating from Urwa bin Zubayr, from Zayd bin Thabit, and he related it. Its isnad is sahih. Amr bin Abu Hakeem is Wasiti, Abu Saeed, known as Ibn Kurdi, and Zubarqan is Ibn Amr bin Umaya Damri.As for his statement, "He would not pray any prayer more intensely..." this is because they complained to the Messenger of Allah about the heat of the burning ground during Ramadan, and they used to pray upon their garments, so it was revealed, "Maintain with care the prayers and the middle prayer and stand before Allah in devout obedience" [Baqarah 2:238], meaning the most excellent one, since the middle one is the best.As for his statement, "And he said, Before it are two prayers and after it are two prayers," it is said that the speaker was Zayd bin Thabit, meaning before it are two prayers, one by day and one by night, and after it are two prayers, one by day and one by night, so the middle prayer is the one that occurs in the middle of the day, which is Dhuhr. This is how Zayd bin Thabit understood it, that the middle prayer is Dhuhr, and when he was asked about the middle prayer he would answer that it is Dhuhr. Ibn Abu Shayba reported this, see Ithaf Khayra (1180).Malik also mentioned this in Muwatta, the chapter on congregation (27), from Dawud bin Husayn, from Ibn Yarbu Makhzumi, who said, I heard Zayd bin Thabit saying, The middle prayer is the prayer of Dhuhr. Ali bin Abu Talib and Abdullah bin Abbas said, as Malik mentioned (28) from them by way of balagh, The middle prayer is the prayer of dawn. He said, "The statement of Ali and Ibn Abbas is the one I like best of what I have heard on this matter."However, what is sahih from Ali and Ibn Abbas is that it is the prayer of Asr, as mentioned previously.