Is marital infallibility (عصمة الزوجية) invalidated if a person is assailed by a tempting thought (وسوسة) to replace the wording of the Qur’an with the Gospel, and he cannot be certain whether he uttered it or not?

What you tell yourself—that intrusive thoughts (waswasa) will make you lose the joy of worship or reading the Quran—does not harm you, nor does anything result from it. Self-talk is forgiven, as is uttering it aloud, because the words of one afflicted with waswasa are spoken without intention. You are rewarded for disliking these intrusive thoughts and being repulsed by them. As Shaykh al-Islam Ibn Taymiyyah said, the believer is tested with the devil's intrusive thoughts, and "that is clear faith" if the servant dislikes them and repels them. This waswasa, despite the intense dislike it causes, is from clear faith, because it is a struggle against Satan. Intrusive thoughts affect people in general, and they increase among those who pray, students of knowledge, and those engaged in worship, because Satan frequently confronts those who seek to draw closer to their Lord. So do not grieve, turn away from the waswasa, and increase in remembrance (dhikr) and obedience.