'Generations' in the Bible

but a witness it is between us and you, and between our generations after us, to do the service of Jehovah before Him with our burnt-offerings, and with our sacrifices, and with our peace-offerings, and your sons do not say hereafter to our sons, Ye have no portion in Jehovah.

And we say, And it hath been, when they say so unto us, and unto our generations hereafter, that we have said, See the pattern of the altar of Jehovah, which our fathers made -- not for burnt-offering nor for sacrifice -- but a witness it is between us and you.