"As for congratulating them on the rituals that are associated with Kufr, then it is unanimously Ḥarām, such as congratulating them on their holidays and practices, and saying: 'Eid Mubarak to you' or expressing joy for the celebration and the like. That is, if the one saying this is free from disbelief, then it is from the prohibited acts. And it is similar to if he congratulates them on their prostration to the cross, for indeed; it is a greater sin in the eyes of Allāh and more detestable than in congratulating the drinking of alcohol, committing murder, engaging in illicit sexual relations and the like."