To live by faith is to live by Spirit and not law.
Galatians 3:12 NASB - 12 However, the Law is not of faith; on the contrary, "HE WHO PRACTICES THEM SHALL LIVE BY THEM."
Romans 3:28-31 NASB - 28 For we maintain that a man is justified by faith apart from works of the Law. 29 Or is God the God of Jews only? Is He not the God of Gentiles also? Yes, of Gentiles also, 30 since indeed God who will justify the circumcised by faith and the uncircumcised through faith is one. 31 Do we then nullify the Law through faith? May it never be! On the contrary, we establish the Law.
Galatians 3:1-9 NASB - 1 You foolish Galatians, who has bewitched you, before whose eyes Jesus Christ was publicly portrayed as crucified? 2 This is the only thing I want to find out from you: did you receive the Spirit by the works of the Law, or by hearing with faith? 3 Are you so foolish? Having begun by the Spirit, are you now being perfected by the flesh? 4 Did you suffer so many things in vain--if indeed it was in vain? 5 So then, does He who provides you with the Spirit and works miracles among you, do it by the works of the Law, or by hearing with faith? 6 Even so Abraham BELIEVED GOD, AND IT WAS RECKONED TO HIM AS RIGHTEOUSNESS. 7 Therefore, be sure that it is those who are of faith who are sons of Abraham. 8 The Scripture, foreseeing that God would justify the Gentiles by faith, preached the gospel beforehand to Abraham, saying, "ALL THE NATIONS WILL BE BLESSED IN YOU." 9 So then those who are of faith are blessed with Abraham, the believer.