—“O you who believe, fight the disbelievers who are nearest to you and let them find you stern, and know that Allah is with those who are mindful of Him.” (al-Tawbah 9:123)

He, blessed and exalted, also says: “They do not set foot in any place that angers the disbelievers, nor do they inflict any injury upon an enemy, without a righteous deed being recorded for them; Allah never lets the reward of those who excel go to waste.” (al-Tawbah 9:120)

Thus, the disbeliever—whoever he may be, whether a Christian, a Jew, an atheist, or even someone who merely claims the name of Islam—is an enemy to Allah, to His Book, to His Messenger, and to all the believers. Whatever cloak he may wear, he remains an enemy.

For that reason, it is impermissible for a Muslim to travel to a land of unbelief unless three conditions are met:

1. He must possess sufficient knowledge to refute the doubts that are cast at him. The disbelievers present Muslims with specious arguments about their morals and about every aspect of the faith, leaving a person hesitant and wavering. It is well established that when a matter demands certainty, harboring doubt in it means one has failed in his obligation. Belief in Allah, His angels, His books, His messengers, the Last Day, and destiny—its good and its evil—must all be held with absolute conviction; whoever doubts any of these tenets is a disbeliever.

Disbelievers deliberately sow such doubts among Muslims. Indeed, one of their leaders once proclaimed, “Do not waste your efforts trying to convert the Muslim to Christianity; it is enough to make him doubt his own religion. If you cause him to doubt, you have stripped him of his faith, and that is sufficient. Drive him out of the fold that grants him supremacy, dignity, and honor—that alone will suffice. As for trying to bring him into Christianity—the religion founded…"