“Their children, who have not known, will hear and learn to fear the LORD your God, as long as you live on the land which you are about to cross the Jordan to possess.”
In context, this verse follows after Moses commanding everyone to get everyone together and read the book of Deuteronomy every seven years. This book is full to bursting with both blessings and curses based on whether the hearer/reader is obedient or disobedient to what God has commanded.
This verse is among those which give a principle: Teach children about God. My daughter is just over a year old and does not have the history with God that her mother and I have. I have seen miracles and have been the recipient of miracles as well. I have seen the fruit of obedience and I have reaped the harvest of disobedience. I have lived enough with God to tell my daughter that God is faithful to those who love Him.
I used to have a coworker who thought that training children up as believers was a disservice to them. This coworker thought that children should be raised to be open-minded and decide for themselves. Since we must each decide for ourselves, that much I agreed with. But The Bible tells me to train up my daughter in the way she should go and promises that she will not depart from the right way when she is old if I have properly trained her. The trouble with a term like “train” is that those who want to make a case against training children will immediately fall back to the idea of training an animal and use that analogy for training children. But those same people (and often, Christians, too) are quick to forget that professional athletes train and weight lifters train and workers receive training. To train or be trained is an excellent thing when done properly.
In order to properly train my daughter and any other children God may bless my wife and me with, I need to do what Moses is telling Israel to do: I need to regularly read The Bible to her/them and remind them of the promises attending obedience and disobedience. I need to recount my personal experience with God to her/them — blessings and discipline, miracles and everyday conversations with God, the results of obedience and disobedience.
The children have not known. It is up to those of us who have walked with God and seen His goodness and the fulfillment of His promises — both agreeable and disagreeable since He promises discipline for disobedience — to tell our children (and grandchildren, when I am older) about what we have tasted and seen in our time with God. They will hear and learn to fear the LORD. That is the one part of this promise to which I will lay any claim, because it is echoed throughout scripture. The children will hear and learn to fear the LORD.