9 For we know that since Christ was raised from the dead, he cannot die again; death no longer has mastery over him.

Read Romans 6:9 Using Other Translations

Knowing that Christ being raised from the dead dieth no more; death hath no more dominion over him.
We know that Christ, being raised from the dead, will never die again; death no longer has dominion over him.
We are sure of this because Christ was raised from the dead, and he will never die again. Death no longer has any power over him.