Deuteronomy 10:20 Thou shalt fear the Lord thy God; him shalt thou serve, and to him shalt thou cleave, and swear by his name.
This response gives the summary and the meaning of the First Commandment. Our response to the Gospel of Salvation is to fear, love, and trust in God above things. This is what believers who have been baptized and have come to faith in Jesus Christ do. This is the response of faith in Christ.
We fear God alone. Alone means that we fear nothing else, like death, disease, demons, and bad things. God delivers us from evil. God is the only source of all good, and we look to Him alone. “Whom shall we fear?” “If God be for us, who can be against us?” Fear nothing but God alone. This kind of trust is not possible for sinners. Everyday worry reveals this truth. Nevertheless, baptized believers are sometimes able to respond with true fear and wholehearted trust by the power of the Gospel and the presence of the Holy Spirit.
When God is feared (trusted) first and only, then we serve Him by serving others; we cleave (hold tight) to Him and His Word of Promise; and we swear by His Name, meaning we pray in Jesus’ name trusting Him alone for help in time of need.
Of course, we fail in keeping the First Commandment, but “there is forgiveness with Thee, that Thou mayest be feared.” The forgiveness of sins keeps us on the path of life.