I heard the Messenger of Allah (ﷺ) say this: Ablution is obligatory (for one who takes anything) touched by fire.
Sahih Muslim Book 3, Hadith 109
← Previous Hadith I and she (the Mother of the Faithful) do it and then take a bath.

Sahih Muslim Book 3, Hadith 108 Next Hadith → I am performing ablution because of having eaten pieces of cheese, for I heard the Messenger of Allah (ﷺ) say: Perform ablution (after eating anything) touched by fire.

Sahih Muslim Book 3, Hadith 110