The Messenger of Allah ﷺ used to offer the Zuhr prayer in midday heat; and no prayer was harder on the Companions of the Messenger of Allah ﷺ that this one. Hence the revelation came down: "Be guardians of your prayers, and of the midmost prayer" (2:238). He (the narrator) said: There are two prayers before it and two prayers after it.  

كَانَ رَسُولُ اللَّهِ ﷺ يُصَلِّي الظُّهْرَ بِالْهَاجِرَةِ وَلَمْ يَكُنْ يُصَلِّي صَلاَةً أَشَدَّ عَلَى أَصْحَابِ رَسُولِ اللَّهِ ﷺ مِنْهَا فَنَزَلَتْ { حَافِظُوا عَلَى الصَّلَوَاتِ وَالصَّلاَةِ الْوُسْطَى } وَقَالَ إِنَّ قَبْلَهَا صَلاَتَيْنِ وَبَعْدَهَا صَلاَتَيْنِ  

The Messenger of Allah ﷺ used to offer the Zuhr prayer in midday heat; and no prayer was harder on the Companions of the Messenger of Allah ﷺ that this one. Hence the revelation came down: "Be guardians of your prayers, and of the midmost prayer" (2:238). He (the narrator) said: There are two prayers before it and two prayers after it. (Using translation from Abū Dāʾūd 411)   

كَانَ رَسُولُ اللهِ ﷺ يُصَلِّي الظُّهْرَ بِالْهَاجِرَةِ وَلَمْ يَكُنْ يُصَلِّي صَلَاةً أَشَدَّ عَلَى أَصْحَابِ النَّبِيِّ ﷺ مِنْهَا قَالَ فَنَزَلَتْ {حَافِظُوا عَلَى الصَّلَوَاتِ وَالصَّلَاةِ الْوُسْطَى} [البقرة 238] قَالَ إِنَّ قَبْلَهَا صَلَاتَيْنِ وَبَعْدَهَا صَلَاتَيْنِ  

[Machine] The Prophet ﷺ used to pray at Al-Hijr or Al-Hajirah, and it was the most difficult prayer for his companions. Then the verse {Maintain with care the [obligatory] prayers and [in particular] the middle prayer and stand before Allah, devoutly obedient.} was revealed. He said, "Because before it there were two prayers and after it there were two prayers."  

أَنَّ النَّبِيَّ ﷺ كَانَ يُصَلِّي بِالْهَجِيرِ أَوْ قَالَ بِالْهَاجِرَةِ وَكَانَتْ أَثْقَلَ الصَّلَاةِ عَلَى أَصْحَابِهِ فَنَزَلَتْ {حَافِظُوا عَلَى الصَّلَوَاتِ وَالصَّلَاةِ الْوُسْطَى وَقُومُوا لِلَّهِ قَانِتِينَ} قَالَ «لِأَنَّ قَبْلَهَا صَلَاتَيْنِ وَبَعْدَهَا صَلَاتَيْنِ»