Amr bin 'Uthman عمرو بن عثمان بن عفان · The Book of the Etiquette of Judges

"The Messenger of Allah said: 'If a judge passes judgment and strives to reach the right conclusion and gets it right, he will have two rewards; if he strives to reach the right conclusion but gets it wrong, he will still have one reward."

That two men referred a dispute to the Prophet concerning an animal, and neither of them had any evidence, so he ruled that it be shared equally between them.