فِي الْحَيَاةِ الدُّنْيَا وَفِي الْآخِرَةِ
In worldly life and in the Hereafter.
Firmness of faith is not confined to earthly trials. The believer whom Allah establishes in faith is able to respond correctly in the grave as well. The report of al-Bara ibn Azib highlights this application of the verse in Surah Ibrahim.
The answer concerns knowledge of one's Lord, faith in the Prophet and religious commitment, not the mechanical memorization of words alone.