Moses wrote this Psalm so it would seem that it would be the earliest Psalm written?
It's the prayer of Moses, a man of God
Psalm 90
1 Lord, you have been our dwelling place
in all generations.
2 Before the mountains were brought forth,
or ever you had formed the earth and the world,
from everlasting to everlasting you are God.
3 You turn us back to dust,
and say, “Turn back, you mortals.”
4 For a thousand years in your sight
are like yesterday when it is past,
or like a watch in the night.
5 You sweep them away; they are like a dream,
like grass that is renewed in the morning;
6 in the morning it flourishes and is renewed;
in the evening it fades and withers.
7 For we are consumed by your anger;
by your wrath we are overwhelmed.
8 You have set our iniquities before you,
our secret sins in the light of your countenance.
9 For all our days pass away under your wrath;
our years come to an end like a sigh.
10 The days of our life are seventy years,
or perhaps eighty, if we are strong;
even then their span is only toil and trouble;
they are soon gone, and we fly away.
11 Who considers the power of your anger?
Your wrath is as great as the fear that is due you.
12 So teach us to count our days
that we may gain a wise heart.
13 Turn, O Lord! How long?
Have compassion on your servants!
14 Satisfy us in the morning with your steadfast love,
so that we may rejoice and be glad all our days.
15 Make us glad as many days as you have afflicted us,
and as many years as we have seen evil.
16 Let your work be manifest to your servants,
and your glorious power to their children.
17 Let the favor of the Lord our God be upon us,
and prosper for us the work of our hands—
O prosper the work of our hands!