A person can still fall into disbelief even while pronouncing lā ilāha illā Allāh. Whoever commits an act of unbelief—even though he says, “lā ilāha illā Allāh, Muḥammad rasūl Allāh”—has performed something that nullifies faith, and the mere utterance of that testimony will not avail him.
That is why the hypocrites used to mention Allah and repeat lā ilāha illā Allāh. When you looked at them, their bodies impressed you; their outward appearance made them seem the very model of perfect believers. They would come to the Messenger ﷺ and say, “We bear witness that you are indeed the Messenger of Allah.” Their statement is reinforced by three emphatic particles—“We bear witness” (nashhadu), the particle inna, and the lām of emphasis in “innaka la-rasūl Allāh.” Yet the Lord of might and majesty, who knows what hearts conceal, declared: “Allah knows that you are truly His Messenger, and Allah bears witness that the hypocrites are surely liars” (al-Munāfiqūn 1). He replied to their testimony with His own, testifying that the hypocrites are lying, and He underscored their falsehood with three emphatic devices of His own. Hence, not everyone who says lā ilāha illā Allāh has his life and property protected, because the Prophet ﷺ made an exception when he said, “except for its due.”
After the Prophet’s ﷺ death, when some Arab tribes withheld the zakāt, Abū Bakr—may Allah be pleased with him—made ready to fight them. Certain Companions objected, saying, “How can you fight people who say lā ilāha illā Allāh?” He replied, “By Allah, I will fight anyone who separates the prayer from the zakāt. Zakāt is the rightful due on wealth, and the Prophet ﷺ said, ‘except for its due.’” He therefore fought them, and Allah granted him victory.
To sum up: uttering lā ilāha illā Allāh alone does not automatically safeguard a person’s blood or property; the accompanying rights must also be fulfilled. Thus the scholars—may Allah have mercy on them—ruled that if an entire village were to abandon the adhān and the iqāmah, they would not be deemed unbelievers, yet they could still be fought and their blood lawfully shed until they resume making the call to prayer and establishing the iqāmah, even though the adhān and the iqāmah are not among the essential pillars.