The Messenger of Allah ﷺ was brought a drink, from which he drank. To his right was a young boy, and to his left were elderly men. He said to the boy, "Do you give me permission to give it to these elders first?"The boy replied, "No, by Allah, I will not prefer anyone over myself for my share from you."So the Messenger of Allah ﷺ placed it in his hand.
حدثني إسحاق بن عيسى حدثنا مالك عن أبي حازم
أن رسول الله ﷺ أتي بشراب فشرب منه وعن يمينه غلام وعن يساره الأشياخ فقال للغلام أتأذن لي أن أعطي هؤلاء فقال لا والله لا أوثر بنصيبي منك أحدا قال فتله رسول الله ﷺ في يده
Its isnad is sahih. It is found in Bukhari 5/102 no. 2451 (Fath al-Bari), in the chapter on injustices, and 5/225 no. 2605 (Fath al-Bari), in the chapter on gifts, and 10/86 no. 5621 (Fath al-Bari), in the chapter on drinks, and Muslim 3/1604 no. 2030, and Ibn Majah 2/1133 no. 3426, both in the chapter on drinks, and Malik in the description of the Prophet ﷺ 2/926 no. 18.