@PainMeridian said
"From the book: "These small "spells" may be used by themselves..." in what context? Not inside a circle as the circle precludes the fiat."
Why do you think that? It does no such thing. Within a properly prepared circle, your word is more powerful.
The main thing I was saying, though, is that a declaration such as "hekas, hekas este bebeloi" may be used by itself to cleanse a space, or may be joined with formal banishing rituals.
"the Latin fiat, meaning "let it be done". Therefore, presumably you are out on a street corner? washing dishes? Gambling?"
LOL. While I wouldn't preclude those, that isn't what I was saying. Yes, you are right, the reason the word was selected was to reflect, "Let it be done!" One accomplishes an action simply by declaring it.
"In what setting does one apply "Asperges me, Dominus, hyssopo, et mundabor lavabis me, et super nivem dealbabor"?"
For any purification, including the purification of a space for formal ritual work.
"I would think the phrase from Liber Legis would be utilized when wants something to occur and then applies the phrase to counter the desire of the result. Is this correct?"
It's too narrow, in that this is not the only situation. But yes, it can be used for that.
To a great extent, the selection is a matter of personal taste and style, as well as the circumstances of the actual rite.
Notice that hekas was used to "banish by fiat" in sample ritual No. 3.