﴿ وَرَبَطْنَا عَلَىٰ قُلُوبِهِمْ إِذْ قَامُوا۟ فَقَالُوا۟ رَبُّنَا رَبُّ ٱلسَّمَٰوَٰتِ وَٱلْأَرْضِ لَن نَّدْعُوَا۟ مِن دُونِهِۦٓ إِلَٰهًۭا ۖ لَّقَدْ قُلْنَآ إِذًۭا شَطَطًا ﴾

“and endowed their hearts with strength, so that they stood up and said [to one another]: "Our Sustainer is the Sustainer of the heavens and the earth. Never shall we invoke any deity other than Him: [if we did,] we should indeed have uttered an enormity!”

The first sentence of verse 14: وَرَ‌بَطْنَا عَلَىٰ قُلُوبِهِمْ (And We made their hearts firm) refers to the event described by Ibn Kathir a little earlier. This tells us that Allah made the hearts of these people firm when the king who was cruel and worshipped idols summoned them in his court and questioned them. This was a matter of life and death. But, despite their apprehension for the worst, Allah Ta` ala made His love, awe and grandeur prevail over their hearts which empowered them to face any eventuality of death or distress. The outcome was that they proclaimed their belief clearly and courageously saying that they did not worship anyone or anything other than Allah and would not do that in future as well. People who firmly resolve to do something for the sake of Allah, this is how they receive help from Allah Ta’ ala.