"Remember, and forget not" is a key phrase in Deuteronomy (9:7). Israel's enjoyment of Canaan would hinge upon their obedience to God. This book reinforces the words of Moses at Sinai 40 years previous. Old and young needed a fresh grasp of the law.
Truth that is not rehearsed will be forgotten; it will cease to be practiced and, eventually, will be rejected. Peter knew this and sought to see believers established in present truth (2Peter 1:12).
Along the way from Egypt to Canaan lessons learned should have safeguarded Israel. There are 13 exhortations in this book to remember things, and nine warnings of things they should not forget.
Amazingly, every day they were to remember their exodus from Egypt (Deut 16:3). In four passages God forcibly stirs their minds by reminding them they used to be slaves.
The first reference is in relation to the Sabbath (5:15). They were to keep it, remembering that in their slavery it was impossible to give God time! Pharaoh was lord of their lives. Though we don't keep a ceremonial Sabbath, we do need to allow time for God in our weekly schedule. Is there hardly time to pray, read our Bibles, or meditate? Is the family altar impossible in modern times? Ex-slaves should make time for God.
Another occurrence is in chapter 15:15, concerning the Hebrew slave set free. The owner was to furnish the ex-slave liberally. Having freely received, when leaving Egypt, they should give freely. These Israelites knew what it was to start out with nothing. Do you have Bible-study resources (stacks of books) that could be more eagerly used by new believers? Perhaps a young couple recently saved from a life of debauchery needs a table or a fridge, or some clothes. Remember the struggles you had at the start; can you help newcomers with theirs? Ex-slaves should be sympathetic to those recently set free.
Third, there was the sanctuary, in chapter 16:11-12. God would choose the place for it and wanted Israel to meet there regularly with Him. It would be a privilege they didn't have in Egypt. The local assembly is dearly loved by God (Acts 20:28; Rev 3:9). It should be a focal point in our lives too. We should not forsake the assembling of ourselves together (Heb 10:25). Assembly meetings should be happy gatherings of ex-slaves rejoicing together in the presence of God.
Finally, Deuteronomy 24:17-22 prescribes the treatment of the stranger and the sorrowful. They were to deal fairly with the foreigner; not how they were mistreated in Egypt. Some of their harvest was to be left in the fields for the widows and orphans. After settling in the land, Israelites could become self-centered. The antidote would be to remember their slavery, when nobody cared about them. Think of others. Remember elderly and sick believers shut away, students in the assembly from far-off lands who feel lonely, as do widows, widowers, and orphans. The most considerate towards the less fortunate should be ex-slaves.