First, I suggest you read www.messiahtruth.com/eternal.html

Quote:
All your words are true; all your righteous laws are eternal. Psalm 119:160

Hidden things may pertain to G-d our L-rd, but that which has been revealed applies to us and our children forever. [We must therefore] keep all the words of this Torah. Deuteronomy 29:28)

"The grass withers, the flower fades; but the word of our G-d will stand forever." Isaiah 40:8.

He remembers his covenant forever. 1 Chronicles 16:15

If you obey G-d your L=rd, carefully keeping all His commandments as I am prescribing them to you today. . . 14 Do not stray to the right or left from all the words that I am commanding you today. [Be especially careful not to] follow other gods or serve them. . .28:15         If you do not obey G-d your L-rd and do not carefully keep all His commandments and decrees as I am prescribing them for you today, then all these curses will come to bear on you. . . 28:46         [These curses] will be a sign and proof to you and your children forever. Deuteronomy 28:1-46

You made your people Israel your very own forever. 1 Chronicles 17:22

And everything that Sarah tells you, listen to her voice. Genesis, 21:12