Although the superscriptions in many of the psalms are not part of the original manuscripts, conservative scholars generally believe they are of value and that they usually reflect what is historically true. Psalm 90 is the only psalm that is attributed to Moses. This would make it the oldest psalm in the book.
Even though it is old, there is a great deal in the psalm that points to NT teachings. It talks about how brief man’s life is. The end of man is to return to dust (Gen 3:19). God, on the other hand, is eternal. In comparing ourselves to God, Moses says, “For a thousand years in Your sight are like yesterday when it is past” (v. 4). Peter probably had his verse in mind in 2 Pet 3:8.
In verses 6-8, Moses refers to the sins of his people, as a result of which they have experienced the wrath of God. Specifically, many of them have died. Most scholars think this is a reference to the rebellion of the Jews at Kadesh Barnea in Numbers 14. Because of their sin, a generation of Jews died in the wilderness and were not allowed to experience victory over their enemies in the Promised Land. This would certainly support the idea that our lives are temporary. The NT teaches us that the wages of sin is death, and that sin brings the wrath of God upon us. God disciplines His children when they sin (Rom 1:18-32; 6:23; Heb 12:5-7).
Moses calls upon the people to recognize their sin. They should appeal to the mercy of the Lord (vv. 13-14). The Lord does the same for us. If we confess our sins, He forgives us of our sins so that we can have fellowship with Him (1 John 1:9).
I find the way Moses ends this psalm particularly interesting. He asks the Lord to “establish the work of our hands” (v. 17). After they acknowledged their sin, they could do the work of the Lord. Even though their lives were short and filled with trouble, they could still do significant things.
In the immediate context of the generation of Jews in Moses’ lifetime, Moses is saying that even in the wilderness this people could serve the Lord. They could do things of value. In their near future, they could experience the blessings of God based upon His compassion. These blessings could be experienced in this life. This was part of the covenant God had made with them. If they obeyed Him, they would be blessed. This was true even though they had previously rebelled against Him.
But certainly, Moses had something bigger in mind. The immediate blessings pointed to even greater ones. The author of Hebrews tells us that Moses understood about eternal rewards in Christ’s coming kingdom (Heb 11:26). Of course, other books in the NT speak of such things as well. Paul says that even though we, too, live in bodies that are dying, believers can work for the Lord and that God will reward such work (1 Cor 15:58).
In verse 12, Moses prays that his people would have a heart of wisdom. Wisdom, in this context, means that they would understand how brief their lives were. As they did, they would realize that the only thing of value is doing what the Lord demands. All things done in disobedience to Him are carried away like a flood (v. 5). The Lord taught the same thing. He told us that when we live for this world, all is lost. Instead, we are commanded to lay up treasures in heaven, in the kingdom of God (Matt 6:19-21).
Psalm 90 is sometimes called a wisdom psalm. Real wisdom is living for the world to come, relying on the mercy of God. Our lives are like a vapor. But because of His mercy, our work can have real value. Moses knew that. We should as well.