It is narrated from Sayyiduna Mu'awiyah (may Allah be pleased with him) that "he saw the Messenger of Allah (peace and blessings be upon him) consume milk; then he (peace and blessings be upon him) prayed (with that same ablution) and did not perform ablution (anew for the prayer)."
The chain of this hadith contains an unnamed (unknown) narrator, because of which it is weak in its chain; however, its meaning is established by other authentic hadith, that consuming things cooked on fire, or milk and the like, does not break ablution.
Hadith Referenceالمطالب العالية بزوائد المسانيد الثمانية / كتاب الطهارة / 152
Hadith Gradingمحدثین:إسناده ضعيف
Hadith Takhrij«حکم الحدیث المطالب العالیہ محققاً تنسیق د. سعد بن ناصر بن عبد العزيز الشَّثري- مکتبہ شاملہ :إسناده ضعيف. » «أخرجه مجمع الزوائد ومنبع الفوائد برقم: 1321»