The journey through the desert was marked by a continuous chain of rebellions. From the time the Israelites left Egypt until the mission of the spies, they repeatedly stumbled, with major failures occurring at places like Taberah, Massah, and Kibroth Hattaavah [מלבי״ם, אברבנאל].
Their defiance was rooted in a rejection of God's laws and rules. Commentators differ on exactly which historical events this rejection points to. One approach suggests it refers to the earliest commandments given at Marah, even before the formal giving of the Torah [רד״ק, אברבנאל]. Another perspective connects this disobedience to other events, such as the sin of the Golden Calf, testing God at Rephidim by refusing to accept the Torah, and directly disobeying the command not to leave any Manna over for the next day [רש״י, אברבנאל].
What made this rejection so severe was the inherent nature of the laws themselves. God's commandments possess a unique power to grant life to those who fulfill them. Yet, instead of embracing this life-giving gift, the Israelites dismissed the laws entirely, treating them as though they had no value [מצודת דוד, ביאור שטיינזלץ].
Beyond rejecting general laws, the people also desecrated the Sabbath. The audacity of their actions is evident in how quickly they failed. They violated the very first Sabbath they were commanded to keep by going out to gather Manna [רש״י, רד״ק, אברבנאל]. This pattern of defiance continued, as the second Sabbath was also deliberately broken by a man gathering wood [מצודת דוד]. This desecration was particularly severe because observing the Sabbath is not merely another rule; it serves as a central testimony to the foundational beliefs of the nation [מלבי״ם].
Faced with this mounting accumulation of sins—both a disregard for the commandments and an assault on the foundations of their faith—God's anger flared. Because of their continuous rebellion, He intended to pour out His wrath and completely destroy the nation while they were still in the wilderness [מלבי״ם, אברבנאל].