To justify Sabbath observance, the Church of God claims that if there was a Sabbath in the Old Testament, there must be a Sabbath in the New Testament. They claim that in the Old Testament, the Sabbath was observed by killing a lamb to sacrifice to God, but in the New Testament, it changed to a form of worship where the Bible was preached, which is an ignorant argument that ignores the Bible. 

All the sacrifices performed in the temple, not just on the Sabbath, were shadows of what Jesus, the heavenly temple, would do, and the lambs taken and offered to God on the Sabbath morning and afternoon were shadows and types of what Jesus would sacrifice.

[Numbers 28:9~10] " 'On the Sabbath day, make an offering of two lambs a year old without defect, together with its drink offering and a grain offering of two-tenths of an ephah of fine flour mixed with oil. This is the burnt offering for every Sabbath, in addition to the regular burnt offering and its drink offering.

Under Old Testament law, a lamb without spot or blemish was offered to God every Sabbath at 9 a.m. and 3 p.m. This sacrifice was for the people, and through it their sins were forgiven. But this was not just Old Testament history, it was a foreshadowing of what Jesus would accomplish. Because Jesus was sacrificed as the lamb of the Sabbath, he was crucified at 9 a.m. and doomed at 3 p.m. Thus, in the New Testament, saints, transformed by God's Holy Spirit without spot or blemish, are sacrificed and martyred for the sins of the people, which is how the Sabbath is observed in the New Testament era.

When Jesus and the early church members broke Sabbath laws prohibiting labor to share the gospel, it was because they wanted to bring true rest to many people. Just as Israel was freed from Egypt and rested in the promised land of Canaan after 40 years in the wilderness, New Testament saints will rest in heaven, which requires martyrdom to enter. Thus, the early church members gave up their bodies as martyrs to enter into eternal rest.

[2 Corinthians5:1~8] Now we know that if the earthly tent we live in is destroyed, we have a building from God, an eternal house in heaven, not built by human hands. Meanwhile we groan, longing to be clothed with our heavenly dwelling,...(8) We are confident, I say, and would prefer to be away from the body and at home with the Lord.

As we've seen, the Old Testament Sabbath was about slaughtering a lamb without spot or blemish and offering it to God, but the New Testament Sabbath is about saints who have been transformed by the Holy Spirit offering their bodies to God and entering into rest. Those who have received the Holy Spirit have the power of God to see sin and transgression, and because they rebuke people for their sins, they are hated or killed. Therefore, in order to enter into eternal rest, we must awaken the churches to repentance.

[John 7:7] The world cannot hate you, but it hates me because I testify that what it does is evil.

[Micah 3:8] But as for me, I am filled with power, with the Spirit of the LORD, and with justice and might, to declare to Jacob his transgression, to Israel his sin.