The Messenger of Allah ﷺ used to eat watermelon with fresh dates and would say, "We break the heat of this with the coolness of that, and the coolness of this with the heat of that."
حدثنا سعيد بن نصير حدثنا أبو أسامة حدثنا هشام بن عروة عن أبيه
كان رسول الله ﷺ يأكل البطيخ بالرطب فيقول نكسر حر هذا ببرد هذا وبرد هذا بحر هذا
[Its chain of transmission is sahih] Tirmidhi collected it in the Book of Foods, Chapter on what has been said about eating watermelon with fresh dates, Hadith 1843, from the hadith of Hisham bin Urwa through this chain, and he said, hasan gharib.