Musnad Ahmad 27:1135

Anas ibn Iyad narrated to us, Umar ibn Abdullah, the freed slave of Ghafra, narrated to us, from Abdullah ibn Umar, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Every nation has its Magians, and the Magians of my nation are those who say: 'There is no Qadar (divine decree).' If they fall ill, do not visit them, and if they die, do not attend their funerals."