Malik Muwatta: Hadith 1490

Yahya said, "Malik said about Jamil ibn Abd ar-Rahman al-Muadhdin that he was present with Umar ibn Abd al-Aziz when he was judging between people. If a man came to him with a claim against a man, he examined whether or not there were frequent transactions and dealings between them. If there were, the defendant could make an oath. If there was nothing of that nature he did not accept an oath from him."

Malik summed up, "What is done in our community is that if some one makes a claim against a man, it is examined. If there are frequent transactions and dealings between them, the defendant is made to take an oath. If he takes an oath, the claim against him is dropped. If the defendant refuses to take an oath, and returns the oath to the claimant, the one claiming his right takes an oath and takes his due."