In Kaddish, we say
“Let Your great Name be sanctified…”
b’alma dee v’ra (in the world that He has created)
NOW, is it:
keer’usaiy (according to His will)
or is it
cheer’usaiy (according to His will)
The general rule is that the 6 letters
have a dagesh in them if they start a word or a syllable. BUT if the previous word ended in:
א ו ה י
and that word connects to the next word conceptually, then there is no dagesh.
In most siddurim, it is cheer’usaiy, because the basic peshat is that it is linked to the previous word v’ra (He has created), which ends with an alef:
“In a world which He has created according to His will.”
BUT the Gra holds that the phrase “according to His will” refers to the beginning of the sentence, yisgadel v’yiskadesh:
“Let His great Name be exalted in the world that He has created, as is His will”
hence, it is keer’usaiy.