Is the bank loan impermissible or not, and what is the wisdom behind its prohibition if it is?

Loans are of two types: 1. Interest-bearing loan: This is forbidden except in cases of dire necessity, based on the Almighty's saying: ﴿O you who have believed, fear Allah and give up what remains [due to you] of interest, if you should be believers. And if you do not, then be informed of a war [against you] from Allah and His Messenger.﴾ [Al-Baqarah: 278-279]. Also, because the Prophet (peace be upon him) «cursed the one who consumes usury, the one who feeds it, its scribe, and its two witnesses, and he said: they are equal.» 2. Interest-free loan: This is permissible; in fact, it is a great act of devotion and virtue, based on the Prophet's (peace be upon him) saying: «There is no Muslim who grants a loan twice but that it is counted as giving charity once.»

Therefore, if the loan is free of interest and not from unlawfully acquired money, it is an act of obedience and righteousness. Otherwise, it is a grave sin.