Allah keeps firm those who believe, with the firm word, in worldly life and in the Hereafter. And Allah sends astray the wrongdoers. And Allah does what He wills.  

يُثَبِّتُ اللَّهُ الَّذِينَ آمَنُوا بِالْقَوْلِ الثَّابِتِ فِي الْحَيَاةِ الدُّنْيَا وَفِي الْآخِرَةِ ۖ وَيُضِلُّ اللَّهُ الظَّالِمِينَ ۚ وَيَفْعَلُ اللَّهُ مَا يَشَاءُ  

This verse: "Allah grants steadfastness to those who believe with firm word," was revealed in connection with the torment of the grave. It would be said to him: Who is your Lord? And he would say: Allah is my Lord and Muhammad is my Apostle ﷺ, and that is (what is implied) by the words of Allah, the Exalted: "Allah keeps steadfast those who believe with firm word in this world and in the Hereafter."  

عَنِ النَّبِيِّ ﷺ قَالَ { يُثَبِّتُ اللَّهُ الَّذِينَ آمَنُوا بِالْقَوْلِ الثَّابِتِ} قَالَ نَزَلَتْ فِي عَذَابِ الْقَبْرِ فَيُقَالُ لَهُ مَنْ رَبُّكَ فَيَقُولُ رَبِّيَ اللَّهُ وَنَبِيِّيَ مُحَمَّدٌ ﷺ فَذَلِكَ قَوْلُهُ ﷻ { يُثَبِّتُ اللَّهُ الَّذِينَ آمَنُوا بِالْقَوْلِ الثَّابِتِ فِي الْحَيَاةِ الدُّنْيَا وَفِي الآخِرَةِ}  

that regarding Allah's saying: Allah will keep firm those who believe, with the word that stands firm in this world and in the Hereafter (14:27). The Prophet ﷺ said: "In the grave, when it is said to him: 'Who is your Lord? What is your religion? And who is your Prophet?'"  

عَنِ النَّبِيِّ ﷺ فِي قَوْلِ اللَّهِ ( يُثَبِّتُ اللَّهُ الَّذِينَ آمَنُوا بِالْقَوْلِ الثَّابِتِ فِي الْحَيَاةِ الدُّنْيَا وَفِي الآخِرَةِ ) قَالَ فِي الْقَبْرِ إِذَا قِيلَ لَهُ مَنْ رَبُّكَ وَمَا دِينُكَ وَمَنْ نَبِيُّكَ؟  

“Allah will keep firm those who believe, with the word that stands firm.” [14:27] This has been revealed concerning the torment of the grave. It will be said to him: ‘Who is your Lord?’ He will say: ‘My Lord is Allah, and my Prophet is Muhammad.’ This is what Allah says: Allah will keep firm those who believe, with the word that stands firm in this world (i.e. they will keep on worshipping Allah Alone and none else), and in the Hereafter (i.e., at the time of questioning in the grave).’” [14:27]  

عَنِ النَّبِيِّ ﷺ قَالَ {يُثَبِّتُ اللَّهُ الَّذِينَ آمَنُوا بِالْقَوْلِ الثَّابِتِ } قَالَ نَزَلَتْ فِي عَذَابِ الْقَبْرِ يُقَالُ لَهُ مَنْ رَبُّكَ فَيَقُولُ رَبِّيَ اللَّهُ وَنَبِيِّي مُحَمَّدٌ فَذَلِكَ قَوْلُهُ {يُثَبِّتُ اللَّهُ الَّذِينَ آمَنُوا بِالْقَوْلِ الثَّابِتِ فِي الْحَيَاةِ الدُّنْيَا وَفِي الآخِرَةِ}  

Al-Bara said about Allah will keep firm those who believe, with the word that stands firm in this world and in the Hereafter "It was revealed concerning the torment of the grave. (Using translation from Nasāʾī 2056)   

{يُثَبِّتُ اللهُ الَّذِينَ آمَنُوا بِالْقَوْلِ الثَّابِتِ فِي الْحَيَاةِ الدُّنْيَا} [إبراهيم 27] قَالَ «نَزَلَتْ فِي عَذَابِ الْقَبْرِ»