Therefore...
Therefore, they said that their Lord was also the same Lord of the heavens and of the earth. Then, they attached to another reasoning and said that their people had taken some gods for worship other than Him. The verse says: “These our people have taken gods other than Him…” Can a belief exist without having any proof and reasoning? Then, why did they not bring a clear proof for the deity of those gods?
The verse continues saying: “…why do they not bring any clear authority regarding them?…” Can an imagination or illusion or a blindly imitation be taken as a proof for such a belief? What a manifest injustice and a great aberration it is! Therefore, the verse says: “…Who is then more unjust than he who forges a lie against Allah?” This ‘calumny’ is an injustice both unto him himself and unto the society wherein he announces this falsehood and he deviates it.
Also, it can be considered as an injustice unto the Pure Essence of the Lord, as well as a disdain unto his Exalted Rank. Those youths, the monotheists, tried to do their best to wipe out the rust of polytheism from the hearts, and to grow the twig of Unity in their place, but the shout of idolatry was so load in that environment that their melodies of Unity were lost in their throats.
Then, in order to deliver themselves from that corruptive environment, and to find a quieter place, they could not help deciding to migrate. Thus, they began consulting with each other. They said among themselves that when they turned away from those idolaters and that which they worshipped besides Allah, and separated their own account from theirs, they should seek refuge in the Cave.
The verse says: “And when you withdraw from them and what they worship save Allah, then seek refuge in the Cave…” It was in that case that their Lord would unfold to them of His mercy and might open to them a way from their difficulty towards calmness, easiness, and happiness.
Then the verse continues saying: “…(and) your Lord will shower on you of His mercy, and furnish you with a gentle issue of your affair.” Explanations The Arabic term /šatata/ means: ‘extravagant separation from truth, and saying a falsehood which by no means is acceptable’. The term /’iftira/ (calumny) involves with the meaning of ‘lie’, yet the word /kaǒiba/ has again been applied in the verse. This application, maybe, is for the fact that there are two kinds of ‘calumny’.