Their Belief in Allah and their Retreat from their People

From here Allah begins to explain the story in detail. He states that they were boys or young men, and that they were more accepting of the truth and more guided than the elders who had become stubbornly set in their ways and clung to the religion of falsehood. For the same reason, most of those who responded to Allah and His Messenger were young people. As for the elders of Quraysh, most of them kept to their religion and only a few of them became Muslims. So Allah tells us that the people of the cave were young men. Mujahid said, "I was informed that some of them wore some kind of earrings, then Allah guided them and inspired them to fear Him, so they recognized His Oneness, and bore witness that there is no god besides Him."

وَزِدْنَـهُمْ هُدًى

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.