yourselves - is a direct object. the "understood" subject is you. [You] prove yourselves to be blah blah
"to be" is just part of the adjectival phrase "to be blameless and innocent"
"blameless and innocent" -see above.
The entire phrase "to be blameless and innocent" is an objective complement, it describes the direct object "yourselves. "
One final thought,
You could just as easily write this sentence without "to be."
" [You] Prove yourselves blameless and innocent." In which case "blameless and innocent" are the objective complement.
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