After having heard an adverse report from the ten spies all the fighting men of Israel refused to enter Canaan and possess it.God condenmed all these men to death in a period of forty years.
Numbers 14:2,4 NASB
2 All the sons of Israel grumbled against Moses and Aaron; and the whole congregation said to them, “Would that we had died in the land of Egypt! Or would that we had died in this wilderness! 4 So they said to one another, “Let us appoint a leader and return to Egypt.”
Then the judgement
Numbers 14:29 NASB
29 your corpses will fall in this wilderness, even all your [o]numbered men, according to your complete number from twenty years old and upward, who have grumbled against Me.
(about 603 550 men died)
But earlier on they had come to mount Sinai and whilst Moses had gone up the mountain to God they had persuaded Aaron to make a golden calf.
Exodus 32:3-4 NASB
3 Then all the people tore off the gold rings which were in their ears and brought them to Aaron. 4 He took this from their hand, and fashioned it with a graving tool and made it into a molten calf; and they said, “[b]This is your god, O Israel, who brought you up from the land of Egypt.”
Then the judgement
Exoduis 32:27 NASB
27 He said to them, “Thus says the Lord, the God of Israel, ‘Every man of you put his sword upon his thigh, and go back and forth from gate to gate in the camp, and kill every man his brother, and every man his friend, and every man his [q]neighbor.’” 28 So the sons of Levi did [r]as Moses instructed, and about three thousand men of the people fell that day.
(about 3 000 men died)
Incidentally by making a golden calf they had broken the second commandment which somehow should have attracted a heavier sentence
Exodus 20:3-5 NASB
3 “You shall have no other gods [b]before Me.4 “You shall not make for yourself [c]an idol, or any likeness of what is in heaven above or on the earth beneath or in the water under the earth. 5 You shall not worship them or serve them; for I, the Lord your God, am a jealous God, visiting the iniquity of the fathers on the children, on the third and the fourth generations of those who hate Me, 6 but showing lovingkindness to thousands, to those who love Me and keep My commandments.
Why was the punishment for refusal to enter Canaan seemingly more severe than that of the golden calf?