It was narrated from Abu Ayyub that the Prophet ﷺ used to perform four Rak’ah before the Zuhr when the sun had passed its zenith, and he did not separate them with a Taslim. He said, “The gates of heaven are opened when the sun passes its zenith.”
أَنَّ النَّبِيَّ ﷺ كَانَ يُصَلِّي قَبْلَ الظُّهْرِ أَرْبَعًا إِذَا زَالَتِ الشَّمْسُ لاَ يَفْصِلُ بَيْنَهُنَّ بِتَسْلِيمٍ وَقَالَ إِنَّ أَبْوَابَ السَّمَاءِ تُفْتَحُ إِذَا زَالَتِ الشَّمْسُ