Are the two noble verses: "And the Day the wrongdoer will bite on his hands [in regret] he will say, 'Oh, would that I had taken with the Messenger a way.'" (Al-Furqan: 27), and "He will say, 'Oh, I wish I had sent ahead for my life.'" (Al-Fajr: 24), specific to disbelievers, or is it permissible to use them as evidence for believers?

The first verse from Surat Al-Furqan, "And the Day the wrongdoer will bite on his hands" (25:27), specifically refers to the disbeliever, though it has been said to include every wrongdoer.

The second verse from Surat Al-Fajr, "He will say, 'Oh, I wish I had sent ahead [some good] for my life!'" (89:24), is inclusive of both the disbeliever and others, though it has been said to specifically refer to the disbeliever.

One can infer from the verse specific to the disbeliever the circumstances of some Muslims who are characterized by regret over neglecting acts of obedience and associating with bad companions.