Hear, O Israel: Yahweh is our God,—Yahweh alone. Thou shalt therefore love Yahweh thy God,—with all thy heart、 and with all thy soul、 and with all thy might;” (Deuteronomy 6:4–5, EMPH)

The word that we translate “Hear” in this passage is the Hebrew word shema.  The Bible Project has an excellent explanation of what the word means:

This verse is the fundamental verse of Judaism and an observant Jew would repeat it more than once a day.  It is also a fundamental verse in Christianity because we see it as foundational to our understanding and to our faith.  It’s as if God is saying: “Hear (and obey) this fundamental commandment: “Thou shalt love the Lord they God with all thy heart, and with all thy soul, and with all thy might.”

The problem of course, is that if we are honest we do not love the Lord our God this way.  We fall short of this commandment, thus we are exposed as the sinners that we are.  This commandment then is also foundational to our understanding of grace.  We could not and cannot keep this commandment perfectly and so we need help.  We have this help in Jesus:

Christ redeemed us from the curse of the law by becoming a curse for us—for it is written, “Cursed is everyone who is hanged on a tree”—” (Galatians 3:13, ESV)