Why does the unknown author of Hebrews attribute authorship of Psalm 95 to David, but in my bible it is not written that the author of it is David?

I wonder why does the unknown author of Hebrews attribute authorship of Psalm 95 to David, but in my bible it is not written that the author of it is David? Was it an error from the unknown author of Hebrews or an error from the spirit which inspired him or not an error at all? > Hebrews 4:7 > > Again, he limiteth a certain day, saying in **David**, **To day, after so > long a time; as it is said, To day if ye will hear his voice, harden > not your hearts**. > > > Psalm 95:7-8 > > For he is our God; and we are the people of his pasture, > and the sheep of his hand. **To day if ye will hear his voice, Harden > not your heart**, as in the provocation, and as in the day of > temptation in the wilderness: