“Hear, O Israel: The Lord our God, the Lord is one. You shall love the Lord your God with all your heart and with all your soul and with all your might.”
Deuteronomy 6:4-5

“And by this we know that we have come to know him, if we keep his commandments. Whoever says ‘I know him’ but does not keep his commandments is a liar, and the truth is not in him, but whoever keeps his word, in him truly the love of God is perfected. By this we may know that we are in him: whoever says he abides in him ought to walk in the same way in which he walked.”
1 John 2:3-6