What is the ruling on the action of a father who gifted a clinic equally to his two sons, then agreed to one son selling his share to the other and authorized him to invest the money to buy another clinic for the absent son, but he has not yet transferred the ownership, and has profited from the money in his possession? And what is the correct action regarding this problem?

If the father has a valid power of attorney that permits him to dispose of his son's money through buying and selling, then what he has done is valid and enforceable. The price for half of the clinic would be what was agreed upon with the father and paid to him. The income from the money belongs to the son, and the clinic becomes the property of the purchaser. As for the father's fear that the son will not return, this does not affect the validity of the contract, and the father must complete the legal procedures. If the son learns of it and disapproves, the sale can be rescinded or a higher price requested, or a new sale contract can be concluded whereby the son buys half of the clinic. This is a good solution for what the father fears. It is advisable to deal with the father wisely and to speak to him with gentle words.