يُثَبِّتُ ٱللَّهُ ٱلَّذِينَ ءَامَنُوا۟ بِٱلْقَوْلِ ٱلثَّابِتِ فِى ٱلْحَيَوٰةِ ٱلدُّنْيَا وَفِى ٱلْءَاخِرَةِ ۖ وَيُضِلُّ ٱللَّهُ ٱلظَّٰلِمِينَ ۚ وَيَفْعَلُ ٱللَّهُ مَا يَشَآءُ
Commentary:
The "firmly established word" is the same which is brought forth by "the good tree" mentioned in v. 25. The verse says that the followers of Islam, which is the good tree mentioned here, will in all ages receive fresh revelation and signs from God which will be a certain means of "strengthening" them.