لِيَزْدَادُوا إِيمَانًا مَعَ إِيمَانِهِمْ
So that they may increase in faith along with their faith. (Qur'an 48:4)
The verse plainly speaks of an increase. The exegetical issue is what precisely increases: the quantity of basic assent, or steadfastness, assurance, its fruits, and the range of matters affirmed?
One interpretation relates the increase to tranquility and firmness granted by God. Another concerns additional knowledge and affirmation of newly explained duties. Neither reading should be assumed without attention to the reasoning offered for it.