The term of 'completion' refers to the act or process of completing or finishing something, the state of being complete or finished. When God Elohim created the heavens and the earth, They had considered how Their children would be formed and had them to rule over the creation. Thus They finished the work in a way of perfectionism, by creating for six days and resting on the Seventh Day from the works, and They designated it as the Sabbath Day, the holy worshiping day for Their people. Whenever we keep the Sabbaths, the eternal rest of thousands over thousands in heaven will befall us and the crowns of life will put on our heads.

The New Covenant Sabbath represents the heaven. When we keep it according to Jesus' teaching, we will enter the kingdom of heaven. By keeping it we can receive abundant blessings from God.

God recorded the Sabbath as one of the Ten Commandments and made us remember and keep it.
We can reflect on God's work of creation through the weekly Sabbath.
The six-day creation contains important messages that we need to know in order to be saved.
The Sabbath is a sign between God and us.
And most importantly, it tells us about God the Father and God the Mother who will save us.
Let's keep the seventh-day Sabbath (Saturday) properly to recognize the Savior(Elohim) who will save us in this age, and to be recognized as God's children!