The permission of the one on right to give the drink to an elder person first

Narrated Sahl bin Sad:

Allah's Apostle was offered something to drink. He drank of it while on his right was a boy and on his left were some elderly people. He said to the boy, "May I give these (elderly) people first?" The boy said, "By Allah, O Allah's Apostle! I will not give up my share from you to somebody else." On that Allah's Apostle placed the cup in the hand of that boy.

حَدَّثَنَا إِسْمَاعِيلُ، قَالَ حَدَّثَنِي مَالِكٌ، عَنْ أَبِي حَازِمِ بْنِ دِينَارٍ، عَنْ سَهْلِ بْنِ سَعْدٍ ـ رضى الله عنه ـ أَنَّ رَسُولَ اللَّهِ ﷺ أُتِيَ بِشَرَابٍ فَشَرِبَ مِنْهُ، وَعَنْ يَمِينِهِ غُلاَمٌ وَعَنْ يَسَارِهِ الأَشْيَاخُ. فَقَالَ لِلْغُلاَمِ " أَتَأْذَنُ لِي أَنْ أُعْطِيَ هَؤُلاَءِ ". فَقَالَ الْغُلاَمُ وَاللَّهِ يَا رَسُولَ اللَّهِ لاَ أُوثِرُ بِنَصِيبِي مِنْكَ أَحَدًا. قَالَ فَتَلَّهُ رَسُولُ اللَّهِ ﷺ فِي يَدِهِ.