“The true name of God is a mystery. It is stated in the Talmud, “And God said unto Moses . . . This is My name for ever (Exodus 3:15). The Hebrew word ‘for ever’ (leolam) is written here in a way that it may be read lealem which means ‘to conceal.’ The name of God is to be concealed.”
“Only once a year, on the Day of Atonement, was the Ineffable Name uttered by the High Priest at the Temple in Jerusalem. And when the name came out of his mouth, ‘in holiness and purity,’ ‘those who stood near him prostrated themselves, and those who stood afar said, “Bessed be the name . . . for ever and ever.”‘ The name was pronounced ten times during the worship, and yet even before the people had left the Temple all of them would forget the pronunciation. According to a medieval source, the name escaped even the High Priest himself as soon as he left the Temple.
To this day the priests close their eyes when pronouncing the blessing, because when the Temple was in existence, they would utter the Ineffable Name . . . and the Shechinah would rest on their eyes. In remembrance thereof they close their eyes.
The Decalogue does not contain any command to worship God. It tells us ‘honor thy father and thy mother,’ it does not tell us, ‘honor they God, worship Him, offer sacrifice to Him.’ The only reference to worship is indirect and negative: Thous shalt not take My name in vain.”
God in Search of Man: A Philosophy of Judaism by Abraham Joshua Heschel