"And Methuselah lived." And why was his name called Methuselah? Because the explicit name of God was written on his sword, and he killed many demons without number. And because he was a righteous man, he lived 969 years, therefore it is stated, "The fear of the Lord prolongs life." (Proverbs 10:27)
The Sword of Methuselah and the Name of God
Midrash Aggadah, Genesis 5:25