Musannaf Ibn Abi Shayba 21:47

Abu Bakr narrated to us, he said: Abu Mu'awiyah narrated to us, from al-A'mash, from Dharr, from Yusi', from al-Nu'man ibn Bashir, he said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Supplication is the worship." Then he recited: "And your Lord said, 'Call upon Me; I will respond to you'"—the verse.