What is the correct meaning of His, the Almighty's, saying: "Indeed, some assumption is sin," and could one of the spouses' interpretations be correct, and what is the ruling on one who errs in interpretation?

Allah Almighty has forbidden the believer from harboring evil suspicions about his fellow believer. Such suspicion is accusing and distrusting people without evidence. Scholars have explained forbidden suspicion as anything for which there is no sound indication or apparent reason. It is forbidden if the person suspected is known for modesty and righteousness. However, it is not forbidden to harbor evil suspicions about someone who is known for engaging in doubtful acts and openly committing evil deeds. The meaning of "suspicion is a sin" is the confirmation and belief in suspicion and persisting in it, not merely what crosses one's mind. Whoever accuses a believer whose outward appearance is righteous, without clear evidence, commits a great sin, and it may amount to slander, which is one of the major sins.