Observation: As Moses instructs the Israelites before the enter the land, he makes this reminder, which is that most of them - and all those in the future - will not have seen what the Lord has done first-hand. He begins with a reminder of the exodus, which almost no one else remembers as those who were alive for it would have been very young. He proceeds with how the Lord cared for them these 40 years in the wilderness, and includes the Lord's miraculous punishments upon those who recently attempted to rebel.
The point is that, in the future, these will just be stories. No one will have witnessed them, and therefore the telling of the stories and the purpose of the Lord must be clear. The Lord has done wonderful, powerful, and miraculous things as a way of saving this nation of priests. In return, they should love the Lord with all their hearts and souls and strength, honor and obey his commands, and put an end to the worship of non-existent idols throughout the land.
That's the lesson ... remember what the Lord has done, even if you haven't seen it for yourself, and respond to his love by faithfully loving him in return and obeying his instructions for life.
Application: This lesson echoes through Jesus to us as Christians, of course. I did not see the crucifixion and resurrection. However, I know how it still impacts my life, and I know that my faith in Jesus and belief in what he accomplished offers me redemption and salvation. I am not as good at returning his love as I should be, but I do believe and I do desire to be better, to love him in return, and to obey his instructions by loving others.
Faith means I am to remember what I never saw, believe what I cannot know, and understand what I didn't learn firsthand. And I do, because ... I perceive what I should not be able to experience. I have seen the work of the Holy Spirit. I know God's own voice. I have learned (some of) the ways of the Lord.
I still struggle to do as I should, and have total faith in everything that will happen in the future. However, I am part of the generations that could never have seen everything the Lord has done, and that Jesus accomplished on the cross, and yet - as Moses instructed - I have learned of his majesty, his mighty hand, and his outstretched arm.
Prayer: Lord, you are everything you have always been, from the great ruler of the universe who parts seas and calms storms and defeats even death, to the father who provides me daily bread and comforts us in times of troubles. I have learned of you. I remember what you have done. Amen.