Is it permissible to conduct a house purchase transaction by paying a down payment one day before signing the contract, without an agreement on the fate of the down payment if the sale is not completed?

The disagreement between the seller and the buyer regarding the fate of the down payment (earnest money) when the sale is not completed does not invalidate the contract. In such a case, recourse is made to custom, for what is known by custom is as if it were stipulated by condition. The Egyptian Dar al-Ifta holds that the earnest money is subject to the agreement of the two parties or prevailing custom. If it is agreed or customary that it should be returned, then it is obligatory to do so. If it is agreed or customary that it should be forfeited, then his right to it is forfeited.