The Prophet used to perform ablution for every prayer, but on the day of the conquest of Makkah, he performed all of the prayers with one ablution.
Sunan Ibn Majah Book 1, Hadith 244
← Previous Hadith "The Messenger of Allah used to perform ablution for every prayer, and we used to perform all of the prayers with one ablution."

Sunan Ibn Majah Book 1, Hadith 243 Next Hadith → "I saw Jabir bin 'Abdullah performing every prayer with one ablution, and I said: 'What is this?' He said: 'I saw the Messenger of Allah doing this, and I am doing as the Messenger of Allah did.'"

Sunan Ibn Majah Book 1, Hadith 245