Zayd bin Khalid ‘Al-Juhaniyyu said: The Messenger of Allah led us in the morning prayer in Hudaybiya ([following a night in which it rained]) Then when he had come out of his prayer, he approached the people, and then said: “Do you know what your Lord has said?” They said: “Allah and His Messenger know best.” He said: “He said: This morning some of my bondservants have become believers in Me and some unbelievers in Me. As for him who said: We have been rained upon by the benevolence of Allah, and His Mercy, that is a believer in me, unbeliever in the star. And as for him who said: We have been rained upon due to such and such star setting at the rising of another [Star foreboding rain], then that is an unbeliever in Me, believer in the star.”
Agreed upon by Al-Bukhari and Muslim. Al-Albani included this hadeeth in The Authentic of Good Sayings as #130.