Paul uses two different commands for yielding: one is a prohibition, the other a positive dedication. What's the difference?
There's a subtle but crucial distinction in how Paul frames our relationship with sin versus our relationship with God.
The Prohibition (to Sin):
'Do not present your members to sin...' This is a command of prohibition. It's about stopping the ongoing act of offering parts of ourselves to sin's control. It acknowledges that sin still tempts and tries to use us, and we must actively refuse to cooperate.
The Dedication (to God):
'...but present yourselves to God...' This is a command of dedication. It's a decisive, once-for-all act of giving our entire being – not just our 'members' but our whole selves – to God's service. This is a response to our new life in Christ.
It's the difference between saying 'No' to the enemy and saying 'Yes' to our King. While we must continually say 'no' to sin's temptations (present imperative), our definitive yielding to God is a completed act (aorist imperative), reflecting our new, permanent status as His.
Our whole being – soul and body – is to be devoted to Him, ready for His use.