“As for those who ignore (God’s signs) -who commit kufr- it is all the same for them whether you warn them or not. They do not believe or trust.” (Al-Baqarah 2:6)
Let us see why any warning does not avail those who commit “kufr”, and why they are called “kafir”.
“When distress seizes you in the sea, whoever you call for help disappears except God. When He brings you back safe to the land, you turn away. The human is ever ungrateful.” (Isra 17:67)
“Surely God does not love anyone who is unfaithful, ungrateful.” (Al-Hajj 22:38)
“God said: What held up you so that you didn’t prostrate when I commanded you?
“I am better than he is. You have created me of fire, and You created him of mud.” (Sad 38:76)
“When We said to the angels, “Prostrate to Adam!”, they thereupon prostrated, except for Iblees. He disdained (to comply with the command), acted arrogantly, and became of the kafir/ignorers.” (Al-Baqarah 2:34)
“My Master! Respite me until the day that they will be raised (from their graves).” (Sad 38:79)
The word “kufr”, thus, can be translated as “ignoring (the truth/God’s commands)”, “ungratefulness”, “disregarding (God’s commands)”, or “disown” depending on the context.
We hereby need to draw attention to one of the facts about traditional Islamic terminology. According to it, a “kafir” is “someone who does not believe in God or in the religion”, but Satan was none of these. He did very well believe in God and the hereafter, and he knew all the facts about worldly life and the afterlife. Yet, he persisted in ignoring God’s command and he acted arrogantly toward Him.
Adam had also disobeyed God’s command when he had eaten from the forbidden tree. However, he had admitted his mistake, turned around from his misdeed, and asked for forgiveness from God (Baqarah 2:37, A’raf 7/22-23). This is why he did not become a “kafir” but Iblis did.
“If you avoid the major (sins) which you are forbidden from, We will cover up your (lesser) faults. We will admit you to an honorable place.” (An-Nisa 4:31)