10 For this is the covenant that I will make with the house of Israel after those days, declares the Lord: I will put my laws into their minds, and write them on their hearts, and I will be their God, and they shall be my people. 11 And they shall not teach, each one his neighbor and each one his brother, saying, ‘Know the Lord,’ for they shall all know me, from the least of them to the greatest. 12 For I will be merciful toward their iniquities, and I will remember their sins no more." 13 In speaking of a new covenant, he makes the first one obsolete. And what is becoming obsolete and growing old is ready to vanish away.
— Hebrews 8:10–13
This is it! Hebrews quotes Jer 31:33-34 here, the most important New Covenant prophecy. With the Old Covenant man does his
own writing, so to speak; he attempts to fulfill the law by his own efforts. Under the New Covenant, under grace, the individual comes to know God for himself; a relationship of faith, hope, and love whereby man and God commune as was always meant to be the case, and then *God *can begin the work of transforming us, of putting His law in our minds and writing it on our hearts. Jesus sums this up simply in John 15:5, “Apart from Me you can do nothing”, echoed in Matt 19:26, “With man this is impossible, but with God all things are possible.”
And the sacraments are formed around this understanding of this relationship so that post #2 can sum up the whole thing in the same vein:
communion with God is essential to man having life at all- and life abundantly, to paraphrase John 10:10. And, if we turn away from God by some serious sin, what happens? We break fellowship and lose communion with Him, so that reconciliation must take place again, with the *sacrament *of Reconciliation, so that we may commune again, by partaking again, of the Eucharist.
Of course we can do this all mechanically, on auto-pilot, without real faith or contrition, etc, in which case the relationship will be compromised, perhaps even non-existent in reality, but in any case the promise of the New Covenant involves
communion, between man and the Trinity, first and foremost.