'Generation' in the Bible

Which the Lord said the children of Israel were to give them, on the day when he made them his priests. It is their right for ever from generation to generation.

Say to Aaron, If a man of your family, in any generation, is damaged in body, let him not come near to make the offering of the bread of his God.

And let this feast be kept before the Lord for seven days in the year: it is a rule for ever from generation to generation; in the seventh month let it be kept.