Is the buyer obligated to pay a commission to the real estate agents who showed him the house, given that the owner had already taken a commission from him without a prior agreement, and the agents' role was limited to showing the property without completing any other procedures?

The basic principle is that the broker does not deserve his commission until his work is completed. However, if custom dictates that merely showing or making an effort is considered a work for which the one who points out or guides deserves something, then they are entitled to what custom dictates, even if the purchase and procedures are completed directly with the owner. This is because what is known by custom is like what is stipulated by condition. But if custom does not dictate this, then they are not entitled to anything.