Musnad Ahmad 588:0

Narrated to us by Yahya ibn Ishaq, who said: Narrated to us by Hammad ibn Salamah, from Humaid, from Anas ibn Malik, that Dhu’ayb Abu Qubaysah came to the Prophet (ﷺ). He said: "O Messenger of Allah, what is the best of deeds?" He replied: "To worship Allah and not associate anything with Him, to establish the prayer, to pay the zakat, to fast Ramadan, and to perform the Hajj to the House." He said: "I have done all of that." He (the Prophet) said: "Then you are a believer, and you are a Muslim."