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^D7736.

Darby Bible Notes

began - 'Since time began' refers to 'holy prophets.' lit. 'his holy since-time-began prophets.'

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.

Strong's

21 Whom ^G3739 the heaven^{G3772 G3303} must^G1163 receive^G1209 until^G891 the times^G5550 of restitution^G605 of all things^G3956, which^G3739 God^G2316 hath spoken^G2980 by^G1223 the mouth^G4750 of all^G3956 his^G846 holy^G40 prophets^G4396 since^G575 the world began^G165.