Related על בבא בתרא 292:7

A man who went to the land beyond the sea, they said to him: Your son died. He began to write all of his property as a gift [to someone else], and afterwards it was known that his son was still alive—his gift stands. Rabbi Shimon ben Menasia says: His gift does not stand, for had he known that his son was alive he would not have done the gift. If he were ill and abed, and they said to him: "Your property is for whom?" He said to them: "I imagined that I would have had a son [by now], but now that I do not have a son, my property is for Ploni"—but afterwards it was known that he has a son, he said nothing. If he were ill and abed and they said to him: "Your property is for whom?" He said to them: "I imagined that my wife would be pregnant [by now], but now that my wife is not pregnant, my property is for Ploni"—but afterwards it was known that his wife is pregnant, he said nothing.