Numbers 14:3
3 And wherefore hath the LORD brought us unto this land, to fall by the sword, that our wives and our children should be a prey? were it not better for us to return into Egypt?
It seems that the Israelites were guilty of idolizing their families. God demands to be at the forefront of our every thought, and we cannot put our families comfort or safety above His word. Not that God would have us presumptuously endanger our children, but when God tells you to do something, you just do it. Their children were never in any danger, and it was wrong for them to doubt God and use their children as an excuse to complain, so He allowed them to witness His preservation of the same children who would go into the land after they were gone.