How To Combine Prayers

It was narrated from Usamah bin Zaid, whom the Prophet ﷺ had seated behind him on his camel on the way from 'Arafah, that when he reached the mountain pass, he dismounted and urinated - and he did not say that he passed water. He (Usamah) said:

"I poured water for him from a small vessel and he performed a light Wudu'. I said to him: 'The prayer.' He said: 'The prayer is still ahead of you.' When he came to Al-Muzdalifah he prayed Maghrib, then they untied the saddles of their mounts and then he prayed 'Isha'."

أَخْبَرَنَا الْحُسَيْنُ بْنُ حُرَيْثٍ، قَالَ حَدَّثَنَا سُفْيَانُ، عَنْ إِبْرَاهِيمَ بْنِ عُقْبَةَ، وَمُحَمَّدُ بْنُ أَبِي حَرْمَلَةَ، عَنْ كُرَيْبٍ، عَنِ ابْنِ عَبَّاسٍ، عَنْ أُسَامَةَ بْنِ زَيْدٍ، وَكَانَ النَّبِيُّ، ﷺ أَرْدَفَهُ مِنْ عَرَفَةَ فَلَمَّا أَتَى الشِّعْبَ نَزَلَ فَبَالَ وَلَمْ يَقُلْ أَهْرَاقَ الْمَاءَ قَالَ فَصَبَبْتُ عَلَيْهِ مِنْ إِدَاوَةٍ فَتَوَضَّأَ وُضُوءًا خَفِيفًا . فَقُلْتُ لَهُ الصَّلاَةَ . فَقَالَ " الصَّلاَةُ أَمَامَكَ " . فَلَمَّا أَتَى الْمُزْدَلِفَةَ صَلَّى الْمَغْرِبَ ثُمَّ نَزَعُوا رِحَالَهُمْ ثُمَّ صَلَّى الْعِشَاءَ .