What is the ruling on a condition that is neither inherent nor beneficial to the contract and does not contradict it?

Primary text

A condition that is not inherent to the contract, not beneficial to the parties, and does not contradict the contract's requirements falls into two types. The first is stipulating a benefit for the seller in the sold item, which has been previously discussed. The second type involves stipulating an entirely separate contract within the initial sale, such as stipulating that upon selling an item, the buyer must sell another item back, or rent, marry, lend money, or transfer the price. Such a stipulation constitutes a void condition which invalidates the entire sale, regardless of whether the seller or buyer stipulated it.