Musnad Abu Ya'la al-Mawsili 129:162

Zuhayr narrated to us, Abdullah bin Bakr narrated to us, Humayd narrated to us, from Anas, that the Prophet (peace and blessings of Allah be upon him) said to a man from Banu al-Najjar: "Accept Islam." He said: "I find myself reluctant." He said: "Accept Islam, even if you are reluctant."