Paul uses the word "letter" to refer to the Old Testament laws because words are made up of letters. The phrase "letter of the law" means every part of the Old Testament laws. AT: "not by obeying the law but as a gift of the Holy Spirit" (See: [[rc://en/ta/man/translate/figs-synecdoche]])
## letter kills ##
This phrase means trying to perfectly obey the Old Testament law and failing will lead to spiritual death. (See: [[rc://en/ta/man/translate/figs-personification]])