Musnad Ahmad Hadith 8191

And the Prophet Muhammad (peace be upon him) said: A man bought a piece of land from another man. The buyer found a pot filled with gold in that land. He went to the one from whom he had bought the land and said, "Take your gold, for I bought the land from you, not the gold." The seller replied, "I sold you the land along with everything in it (so the gold belongs to you)." Both of them took their dispute to a third man for a decision. The arbitrator asked, "Do either of you have children?" One said, "I have a son," and the other said, "I have a daughter." The arbitrator said, "Marry the boy to the girl and spend the gold on both of them as charity."