9 For all our days are passed away in thy wrath: we spend our years as a tale that is told.
10 The days of our years are threescore years and ten; and if by reason of strength they be fourscore years, yet is their strength labour and sorrow; for it is soon cut off, and we fly away.
Psalm 90 is the only Psalm that is clearly identified as a Psalm of Moses. We don’t know when he wrote it, but it was almost certainly at the time of the Exodus or later.
And Moses was fourscore years old, and Aaron fourscore and three years old, when they spake unto Pharaoh.
Moses was probably at (or past) the outer limit of 80 years that he described in Psalm 90 at the time he wrote it.
So teach us to number our days, that we may apply our hearts unto wisdom.
Moses continued to “number his days” until the age of 120.
And Moses was an hundred and twenty years old when he died: his eye was not dim, nor his natural force abated.
May God give us grace to apply our hearts unto wisdom through all the days He gives us to number.