When asked, Jesus told us the greatest commandment. It is, "Hear, O Israel, the Lord lis God, the Lord alone."
We find it in Chapter Six of the Book of Deuteronomy.
I heard someone giving the Hebrew of that. It was, "Shma, Israel, Adonai, elohim, Adonaii acham."
The first word, "Hear," was much weaker than the Hebrew's "Shma" which not only "Hear," but. . "Be quiet, and listen!"
Another oddity of this most famous of Hebrew saying was that where Jews say, "Adonai," what is written there is "YHWH." That was God's personal name, Yahweh, but it was never pronounced, because the people feared breaking the commandment against taking the Lord's name in vain.
Back then Jewish people wrote only their consonants, leaving it to the reader to remember the vowel sounds. That being the case, and with their fearing taking the Lord's name in vain, thy forgot that the YHWH stood for Yahweh. Some people guessed that the missing letters made God's name Jehovah.