Albert Barnes on Romans 8:12

We are debtors. We owe it as a matter of solemn obligation. This obligation arises

(1.) from the fact that the Spirit dwells in us;

(2.) because the design of his indwelling is to purify us;

(3.) because we are thus recovered from the death of sin to the life of religion; and he ,who has imparted life, has a right to require that it be spent in his service.

To the flesh. To the corrupt propensities and passions. We are not bound to indulge them, because the end of such indulgence is death and ruin, Rom 7:21,22. But we are bound to live to God, and to follow the leadings of his Spirit, for the end is life and peace, Rom 7:22,23. The reason for this is stated in the following verse.

(q) "not to the flesh" Ps 116:16