Sayyiduna Anas bin Malik (may Allah be pleased with him) narrates from the Prophet of Allah (peace and blessings be upon him) that he (peace and blessings be upon him) said: "Two men were crossing a desert: one was a worshipper and the other was a sinner. The worshipper became so thirsty that he collapsed from exhaustion. His companion began looking at him, and he had with him a vessel for ablution in which there was a little water. Seeing him lying there, he began to say (to himself): 'By Allah! If this righteous servant dies of thirst while I have water with me, I will never receive any good from Allah; and if I give him my water to drink, I myself will die.' So he put his trust in Allah and made up his mind; he sprinkled some of the water on him and gave him the rest to drink, whereupon he stood up and the two of them crossed the desert. Then on the Day of Resurrection that sinful man will be made to stand for the reckoning, and he will be ordered to the Fire, and the angels will drive him along. Then he will see the worshipper and call out: 'O so-and-so! Do you not recognise me?' He will say: 'Who are you?' He will say: 'I am that so-and-so who preferred you over myself on the day in the desert.' He will say: 'Yes, I recognise you.' Then the worshipper will say to the angels: 'Stop!' So they will stop, and he will come and supplicate to his Lord, the Mighty and Majestic, saying: 'O my Lord! You know the favour he did me, and how he preferred me over himself; O Lord, grant him to me.' Allah Almighty will say: 'He is yours.' Then he will come, take his brother by the hand and admit him into Paradise."
Ja'far bin Sulayman (may Allah have mercy on him) said: I asked Abu Zilal (may Allah have mercy on him): "Did Sayyiduna Anas (may Allah be pleased with him) narrate this hadith to you from the Messenger of Allah (peace and blessings be upon him)?" He said: "Yes."
Imam al-Tabarani (may Allah have mercy on him) said: "No one narrated this hadith from Abu Zilal except Ja'far, and al-Salt is alone in narrating it."
Hadith Referenceالمعجم الأوسط / باب الألف / 2906
Hadith Takhrij«أخرجه أبو يعلى فى «مسنده» برقم: 4212، وابن حجر فى «المطالب العالية» برقم: 4583»