What if we don’t think about our limitations? What if we don’t consider the reality of our coming death and what comes afterwards? We’re probably going to be busy living for ourselves, plunging into pleasure and pursuing everything we can accomplish. We won’t think about God’s judgment or the consequences of what we do.

Psalm 90 isn’t very cheerful.

It is Moses’s meditation on the sinfulness and weakness of human life. Perhaps you can imagine an old Moses offering this prayer near the end of his time on earth.

The Psalm title calls him “the man of God.” That reminds us that Moses was the one chosen to lead God’s people out of bondage in Egypt and into the Promised Land. He had witnessed the terrible sufferings of God’s people. He’d experienced God’s mighty acts of deliverance. But Moses had also tasted the bitterness of Israel’s uprisings in the desert and the LORD’s just judgment on his people.

Over all those years, what had Moses learned? He’d learned about sin. About Israel’s sin, and about his own. That even when we have the best of intentions, our inherent weakness can hinder us in doing what’s right. And he had learned that every sinner deserves God’s holy wrath—Moses deserved it too.

In those years Moses also learned about the frailty of life. Think about the thousands of Israelites fallen in the desert: in battle, from snake bites, even consumed by God’s fire. Consider too, the forty years of wandering: God was just waiting for that sinful generation to die off. Wherever they went in the wilderness, the Israelites left graves behind them.

So compared to the everlasting God, Moses sees that mankind is almost nothing: “You carry them away like a flood; they are like a sleep. In the morning they are like grass which grows up: in the morning it flourishes and grows up; in the evening it is cut down and withers” (Ps 90:5-6).

Viewed from one angle, that’s the nature of our existence: nasty, brutish, and short. We are born weak, spend our life sinning, and then we die, each one.

Psalm 90 can seem a bit jarring, especially if we’re optimistic about our life and the prospects of a new year. There’s more here, of course, for there is good news in this psalm, even the gospel of Christ. And it’s in light of everything we know about this life that Moses teaches us to pray in verse 12:

Teach us to number our days.

What is numbering? In a way, it’s as simple as a kindergarten exercise in math. You number the apples, or count the blocks, and you write down the answer. Well, we also have to number our days! But unlike counting apples, this is something we need help with: “Teach us, O God!” We’re not asking God to reveal how long we’re going to live. We pray that God will help us contend with the fact that our days of life are short.

When you’re a kid, of course, time seems to stretch on forever. Two months of summer vacation seem endless! But when you get older, a decade passes by in a flash. Suddenly you’re the senior guy at the office, or all the kids have moved out, and you ask, “Where did the time go?”

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