Deuteronomy 6:5 (BSB)

And you shall love the LORD your God with all your heart and with all your soul and with all your strength.

From Deuteronomy 6. Also in the ESV.

Commentary on Deuteronomy 6:5

• Matthew Henry (Presbyterian), Matthew Henry's Complete Commentary on Deuteronomy 6:4-16: Here is, I. A brief summary of religion, containing the first principles of faith and obedience, Deu 6:4, Deu 6:5. These two verses the Jews reckon one of the choicest portions of scripture: they write it in their phylacteries, and think themselves not only obliged to say it at least twice every day, but very happy in being so obliged, having this saying among them...
• John Gill (Reformed Baptist), Exposition of the Old and New Testaments on Deuteronomy 6:5: And thou shalt love the Lord thy God,.... Which is the first and chief commandment in the law, the sum and substance of the first table of it; and includes in it, or at least has connected with it, knowledge of God, esteem of him, delight in him, faith and trust in him, fear and worship of him, and obedience to him, which when right springs from it.
• Keil & Delitzsch (Lutheran), Biblical Commentary on the Old Testament on Deuteronomy 6:5: Deu 6:5 As the one God, therefore, Israel was to love Jehovah its God with all its heart, with all its soul, and with all its strength. The motive for this is to be found in the words “thy God,” in the fact that Jehovah was Israel’s God, and had manifested Himself to it as one God.