What is the religious ruling regarding someone who harbored ill suspicions about her sister's husband, then informed her sister of these ill suspicions without proof, knowing that the husband is innocent and adheres to his religion, and the wife believes her sister? And what do you advise each of the husband, the wife, and the sister?

Lying about people and falsely accusing them without proof is forbidden calumny according to Sharia, based on the Almighty's saying: "And that they will not produce any calumny that they might have fabricated between their hands and their feet." And the Almighty's saying: "And those who harm believing men and believing women for [deeds] they did not earn have certainly borne slander and a manifest sin."

If the matter is as stated, then the sister has combined calumny and tale-bearing. She must repent and rectify what she has corrupted by discrediting herself to her sister, seeking forgiveness, and praying for her sister's husband. As for the wife, she must defend her husband and prevent her sister. The husband must be patient and avoid suspicious situations.