Some believe that the Old Testament was physical as opposed to the New Testament, which is all spiritual. This is an over-simplification at best or, more precisely, dead wrong. Certainly, the Mosaic Covenant was more specific in many ways, whether consecrating for worship or serving in life, but God has always wanted His people’s heart. He does not change (Malachi 3:6) and even when His covenant changes, His nature does not. Therefore, a change of law (Hebrews 7:12) does not indicate a change of heart. He has always wanted His people to worship and live with spiritual, heart-involved commitment (Joel 2:13), regardless of the physical fulfillment of His commands (John 4:23-24).
An interesting outward sign of the various Mosaic devotions was when Moses, after killing the sacrificial ram, “put some of the blood on the tips of their (Aaron and his sons) right ears, on the thumbs of their right hands, and on the big toes of their right feet.” From the time of Aaron, and the priests who followed him from then on, it was an outward sign of an inward loyalty. In spite of these visible indicators, however, “the Levites went astray” (Ezekiel 48:11).
I know a man, taught from youth about the God’s love in Christ. He was active in the Lord’s work for many years. In fact, in his dedication (coupled with modern culture), he had a blood-red, drop tattooed on his right ear lobe, his right thumb and his right big toe. I thought it was a bit extreme but admirable nonetheless; his outward sign of an inward commitment. Until, one day, he left Christ. The tattoos are faded but the dedication is gone and, as far as I know, he has no relationship with God. It breaks my heart.
We cannot always tell what is going on in the mind of a man. Sure, “by their fruits, you will know them” (Matthew 7:20) but good actors are difficult to discover. Actual obedience, “doing the will of God from the heart” (Ephesians 6:6), indicates what is at the root of the matter. What is on the inside usually comes out sooner or later because it comes from the heart. So, “keep your heart with all diligence, for out of it spring the issues of life” (Proverbs 4:23).