Musnad Ahmad 652:6

'Abd al-Razzaq narrated to us, Sufyan informed us, from al-A'mash and Mansur, from Dharr, from Yusi' al-Kindi, from al-Nu'man ibn Bashir, that the Messenger of Allah (may Allah bless him and grant him peace) said: "Verily, supplication is worship." Then he recited: "Call upon Me; I will answer you. Indeed, those who disdain My worship will enter Hell [rendered] contemptible." [Ghafir: 60]