Deuteronomy 29:29 meaning

In this verse, Moses seems to be answering the question raised in v. 24 (Why has the Lord done thus to this land?). This is a question asked by neighboring nations in the future, after the land has been ravaged, due to Israel's disobedience of their covenant with their Suzerain God (Deuteronomy 29:22-28). It is worth noting that this provision of this additional covenant, which adds to the first (Deuteronomy 29:1), is being given while Israel is still in Moab, preparing to enter and take the land. This prophecy is for a time subsequent to Israel possessing the land (Deuteronomy 29:22). It thus serves as both a warning to future generations, as well as a comfort to the current generation, in that it presumes certainty that Israel will, in fact, possess the land.

This question will be asked in the future "How could Israel, the recipient of eternal promises of being the LORD's servants, experience such destruction and exile from the Promised Land?" The human answer was given in Deuteronomy 29: 25-28, but here in Deuteronomy 29:29 Moses provided the LORD's answer in the form of a proverb. It is given in two parts.

The first part of the proverb states that the secret things belong to the Lord our God (v. 29). The secret things here indicates that there are things the Suzerain (Ruler) God chooses not to reveal to His covenant people. There is some knowledge that God keeps to Himself. Part of the reason for this is that we as humans simply cannot fathom the things of God, as His thoughts and ways are beyond our ability to fathom (Isaiah 55:8-9; Romans 11:33). God is God, and knows many things He does not reveal. We might think of God as being like a parent, who reveals things to their children on a basis that is age-appropriate.

The Israelites did not have access to the facts and knowledge God chose to retain as secret things, for His own reasons. Such knowledge and facts are mysteries to mankind. However, God chose to reveal ample information to allow humans to make an informed choice.

The second part of the proverb concerned the things revealed. These are the precepts that were clearly stated and written for Israel in the covenant between them (Israel) and God, their ruler. Thus, that which was revealed belong to us and to our sons forever, the purpose of which was that they may observe all the words of this law. What God had revealed to Israel in His laws was sufficient to give them ample reason to live a holy life, in accordance with His will. God makes clear throughout that all these laws are given for their good, that their land might be blessed (Deuteronomy 4:37; 7:7). A parent gives ample information to their child to instruct them in ways that are for their good, but keeps the information at the level of the child.

God's relationship with New Testament believers follows a similar pattern to that which is laid out in Deuteronomy. This is no surprise, since God is unchanging (Hebrews 13:8). Just as God chose Israel because He loved them (Deuteronomy 4:37; 7:7) God takes all as His who believe on Jesus Christ, giving them a new birth into His family. He does this because He loves all people (John 3:5, 14-16). This acceptance is complete and unconditional, being rooted in Jesus's death on the cross. It was upon that cross that every sin of humanity was nailed (Colossians 2:14). In both cases, of Israel and New Testament believers, God's acceptance is a given.

Then, just as with Israel, God has a covenant with New Testament believers. It is a new covenant, written upon the hearts of believers (1 Corinthians 11:25; 2 Corinthians 3:6-7; Hebrews 8:7-13). This covenant has a similarity that our choices as believers determines whether we receive blessings (positive consequences) or cursings (negative consequences). The apostle Paul states the principle in his letter to the Galatians that

"…whatever a man sows, this he will also reap. For the one who sows to his own flesh will from the flesh reap corruption, but the one who sows to the Spirit will from the Spirit reap eternal life."
(Galatians 6:7b-8)

In this verse Paul calls the blessings "eternal life." The Greek word "aonios" translated here as "eternal" means "from the beginning of or to the end of the age." An example of "beginning" is in Romans:

"Now to Him who is able to establish you according to my gospel and the preaching of Jesus Christ, according to the revelation of the mystery which has been kept secret for long ages past ("aonios")"
(Romans 16:25)

The Greek word "zoe" translated "life" in the phrase "eternal life" indicates a high quality or experience of life. So the phrase "eternal life" has the same basic idea as the blessings God sets forth in His covenant with Israel, the idea of an abounding abundance. However, just as the New Testament is a covenant written on the heart, the promised New Testament blessing is primarily spiritual. As Jesus stated in His vocal prayer to His Father in John 17:

"This is eternal life (Greek, "aonios zoe"), that [His followers] may know You, the only true God, and Jesus Christ whom You have sent."
(John 17:3)

For a New Testament believer, to know God through a walk of obedience in faith is the equivalent of Israel keeping its covenant. To walk in faith leads to knowing Jesus, and that is the way to the greatest possible benefit/reward that life affords (eternal life).

Peter told his readers that the LORD's "divine power has granted to us everything pertaining to life and godliness" (2 Peter 1:3). Given that "life and godliness" are probably a hendiadys (opposites that indicate a totality), Peter is saying that the LORD has revealed to believers everything they need in order to live a godly life.