Musnad Ahmad 30:852

Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, from Muhammad ibn Ziyad, from Abu Hurairah, from the Prophet, peace and blessings of Allah be upon him, that he said: "I truly hope that if my life is prolonged, I will meet 'Isa ibn Maryam. But if death hastens to me, then whoever among you meets him, let him convey my greeting of peace to him."