It is narrated from Abu al-Bakhtari that on the day of Siffin, when the heat grew very intense, Sayyiduna Ammar bin Yasir (may Allah be pleased with him) said (due to the severity of his thirst): "Bring me something to drink." Then he said: "Indeed, the Messenger of Allah (peace and blessings be upon him) said: 'The last drink you will drink in this world will be a draught of milk.'" After that he advanced (onto the battlefield) and was martyred.
Imam Abu Bakr bin Abi Shaybah recorded it, and Imam Abu Ya'la also narrated the like of it through his own chain via Sufyan.
Hadith Referenceالمطالب العالية بزوائد المسانيد الثمانية / كتاب الفتوح / 4422
Hadith Gradingمحدثین:إسناده ضعيف، منقطع
Hadith Takhrij«حکم الحدیث المطالب العالیہ محققاً تنسیق د. سعد بن ناصر بن عبد العزيز الشَّثري- مکتبہ شاملہ :إسناده ضعيف منقطع » «أخرجه مسند أحمد برقم: 18401، وأخرجه إتحاف الخيرة المهرة بزوائد المسانيد العشرة برقم: 6893/1»