Albert Barnes Commentary Psalms 78:3

"Which we have heard and known, And our fathers have told us." — Psalms 78:3 (ASV)

Which we have heard and known – Which have been communicated to us as certain truth.

And our fathers have told us – That is, we have heard and known them by their telling us; or, this is the means by which we have known them. They have come down to us by tradition from ancient times.