Specifically, the Yod י of ShaDaY – it is the tip of the Dalet ד of EḤaD∞‘One’, and if he is false, the tip of the Dalet ד of EḤaD is removed, and there remains AḤeR∞‘another’.
And because of this, the verse says: (Ex. 34:14) For you shall not bow down to another god etc... And at the time when there rules over a person a demon – who is ‘another god’ – he becomes enslaved to it with all kinds of afflictions. And this sin causes Israel to become enslaved, by the nations of the world.
And whoever protects the sign of covenant, in which ever place it is, whether the covenant of circumcision, whether Sabbath and Festivals, the blessed Holy One protects him, because of it, in every place, and shields him from his enemies, like Moses, of whom it is stated: (Ps. 91:1)... in the shadow of ShaDaY (Almighty) he will abide...