Musnad Ahmad 30:1234

Abu al-Nadr narrated to us, he said: al-Mubarak narrated to us, from al-Hasan, from Abu Hurayrah—I think he mentioned it from the Prophet, peace and blessings be upon him—: "The enslaved servant shall be brought to account for his prayer. If he has diminished anything from it, it will be said: 'Why did you diminish it?' He will say: 'O Lord, You empowered a master over me who kept me busy from my prayer.' He will say: 'I saw you stealing from his wealth for yourself, so why did you not steal for yourself from your deeds, or his deeds?'" He said: "Then Allah establishes the proof against him."