All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
This statement does not have any effect on the marriage of that man with that woman at all. Even if he says it while she is already married to him, it does not have any effect on their marital life.
In fact, the wife being concerned with her husband and her fulfilling his rights is something Islamically required and this strengthens the marital relationship between them. This is indeed among the great objectives of the Sharee’ah. Allaah Says (what means): {And due to them [i.e. the wives] is similar to what is expected to them, according to what is reasonable.}[Quran 2:228] Allaah also Says (what means): {And live with them in kindness.}[Quran 4:19]
However, a husband should balance between the rights of his mother and the rights of his wife. For more benefit, please refer to Fataawa 86430 and 99471.
Allaah Knows best.