Sahih Bukhari: Hadith 4547

Regarding the Verse: "And among men is he who worships Allah's as it were on the very edge." (22:11). A man used to come to Medina as if his wife brought a son and his mares produces offspring. He would say, "This religion (Islam) is good," but if his wife did not give birth to a child and his mares produced no offspring, he would say, "This religion is bad."