If the buyer and seller agreed upon a sale and the buyer paid a down payment (ʿurbūn), then the buyer reneged on the purchase, is the seller entitled to keep the down payment?

It is permissible to take earnest money (deposit) in a sale if the seller and buyer agree to it. This is the madhhab (legal school of thought) of Imam Ahmad and Umar ibn al-Khattab, may Allah be pleased with him. Sheikh Ibn Baz issued a fatwa allowing it, and the Permanent Committee stated that earnest money sales are permissible. This is when the buyer pays an amount less than the full price of the item after the contract to secure the merchandise. If he takes it, the earnest money is counted towards the price, and if he does not take it, the seller is entitled to keep it. The narrated hadith prohibiting earnest money sales is weak.