Hebrews 3:12-19 is a commentary on the quotation in 7-11 (from Psalm 95). The author encourages his audience to take care that there be none among them with an unbelieving heart that falls away from the living God. Becoming partakers of Christ means holding firm the beginning of our assurance until the end. If we take the original audience to be primarily Jewish minded individuals (which I believe is warranted by the text), what is the “beginning of our assurance”? Is it referring to, in general, a knowledge of the gospel message or is this beginning a faithfulness to Judaism with its object being Christ? Is “the end” entering into “God’s rest” in the present (the salvation rest and inheritance we have in Christ) or the future eternal “Sabbath rest”?