NET
21 This one heaven must receive until the time all things are restored, which God declared from times long ago through his holy prophets.
Darby
21 whom heaven indeed must receive till [the] times of [the] restoring of all things, of which God has spoken by the mouth of his holy prophets since time began.
KJV
21 Whom the heaven must receive until the times of restitution of all things, which God hath spoken by the mouth of all his holy prophets since the world began.