Musar zu Wajikra 21:23

This should give you some idea of the power that lies within a chazzan, who unites within him these three Names. But if the chazzan is lightheaded and does not pray with the intention to fulfill the congregation’s obligation, then he sullies these three holy Names. This is reckoned as if he made blemishes in the sacrifices because in our times prayer takes the place of the sacrifices. I have found it written in the name of the scholars of earlier generations that there is an esoteric allusion hidden within the verse, “Return to your rest, O my soul, for Hashem has dealt bountifully with you” (Tehillim 116:7). Among the letters of this verse are the letters of the Divine name מו"ם (part of the seventy-two letter name; see Rashi, Sukkah 45a). Therefore, if one recites the word “rest” hurriedly and without enunciating it properly, one blemishes this name and in consequence is denied rest in the World to Come! This same Divine Name (מו"ם) is alluded to in the initial letters of the phrase from the Morning Service, “He fashions servants and His servants, etc.” A mnemonic to help one bear in mind not to blemish one’s prayers is the sentence, “For there is a blemish in it, it is abominable, it will not find favor as a sacrifice to Hashem” (a composite of Vayikra 21:23, 19:7 and 22:27). And since in our times prayer is in place of the sacrifices whoever swallows letters in his prayers is reckoned as if he made blemishes in the sacrifices.