The whispers of the Shaytaan have increased in my prayer
The whispers (of Shaytaan) have increased in (my) prayer. Does it invalidate my prayer?
No, it does not invalidate your prayer. However, it lessens the reward; and the reward of the prayer is not written for you except in that part in which I your heart was present.
Question answered by the Esteemed scholar Shaykh Saalih bin Fawzaan al-Fawzaan.