If you are asking whereabouts in the Bible this idea is expressed, you'll find it in Psalm 90 Verse 10 which reads: "The days of our years are threescore years and ten..."
If you are asking what it means, a score = 20, so threescore and ten = 70...that being the average lifespan.
New Forester...Firstly David lived to be 70 years old. His death was in 965BC. However, Psalm 90 is attributed to Moses.
I do like your expertise in other forums. Thank you for your interesting answers.