Psalm 40:8
I delight to do Thy will, O my God: yea, Thy law is within my heart.
Service, true service, for Christ comes from a believer who delights to do the will of the Lord. Intelligent service comes from a person whose heart retains the Word of the Lord. You can’t know His will unless His Word abides in you. You can’t truly serve Him unless it’s genuine service from a heart of love for Christ.