God is the Creator and absolute ruler of the universe. He is eternally existent in three personalities: the Father; the Son and the Holy Spirit. These three are co-equal and are one God. ~ Genesis 1:1, 26-27; 3:22; Psalm 90:2; Matthew 28:19; 1 Peter 1:2; 1 Corinthians 13:14
What Dr. Rice means here is that as far as mankind goes, even the best of us are still crooked sinners saved by grace yet God in His graciousness gives us the glorious privilege of serving Him. None of us deserve to be used by God.