Should goods be sold if a third party has accused them of theft without verifying the validity of the claim?

If you are certain or it is highly probable that the merchandise is stolen, then it is not permissible for you to sell it, because that would be aiding in sin and aggression. Its price would be unlawful because your client does not own it. However, if you have doubts about the veracity of the information, then it is better to refrain from selling it and to return it to its owner, based on the Prophet's (peace and blessings be upon him) saying: "Whoever avoids doubtful matters has cleared himself in regard to his religion and his honor," and his saying: "Leave that which makes you doubt for that which does not make you doubt." Acting with caution in this situation is more appropriate and absolves one's responsibility.