If a person allows another to have his right
باب إِذَا أَذِنَ لَهُ أَوْ أَحَلَّهُ وَلَمْ يُبَيِّنْ كَمْ هُوَ
Sahih al-Bukhari, Book of Oppressions(view book)
Sahih al-Bukhari 2451
Narrated Sahl bin Sad As-Sa'idi:
A drink (milk mixed with water) was brought to Allah's Apostle who drank some of it. A boy was sitting to his right, and some old men to his left. Allah's Apostle ﷺ said to the boy, "Do you allow me to give the rest of the drink to these people?" The boy said, "O Allah's Apostle! I will not give preference to anyone over me to drink the rest of it from which you have drunk." Allah's Apostle then handed the bowl (of drink) to the boy. (See Hadith No. 541).
حَدَّثَنَا عَبْدُ اللَّهِ بْنُ يُوسُفَ، أَخْبَرَنَا مَالِكٌ، عَنْ أَبِي حَازِمِ بْنِ دِينَارٍ، عَنْ سَهْلِ بْنِ سَعْدٍ السَّاعِدِيِّ 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 لاَ وَاللَّهِ يَا رَسُولَ اللَّهِ لاَ أُوثِرُ بِنَصِيبِي مِنْكَ أَحَدًا. قَالَ فَتَلَّهُ رَسُولُ اللَّهِ ﷺ فِي يَدِهِ.