10. For in that he died, he died unto--that is, in obedience to the claims of
      sin once--for all.
      but in that he liveth, he liveth unto--in obedience to the claims of God.
      God--There never, indeed, was a time when Christ did not "live unto God." But in the days of His flesh He did so under the continual burden of sin "laid on Him" (Isa 53:6; 2Co 5:21); whereas, now that He has "put away sin by the sacrifice of Himself," He "liveth unto God," the acquitted and accepted Surety, unchallenged and unclouded by the claims of sin.

JFB.