G2480–ἰσχύω–ischuō

for a covenant over dead victims `is' stedfast, since it is no force at all when the covenant-victim liveth,

ἰσχύει ischuei “it is in force”

Be confessing to one another the trespasses, and be praying for one another, that ye may be healed; very strong is a working supplication of a righteous man;

ἰσχύει ischuei “prevails”

and they did not prevail, nor was their place found any more in the heaven;

ἴσχυσεν, ischusen “he had [enough] strength,”