The meaning of the word perfect in the bible is not the English definition of the word as in sinlessness/unblemished.. but something coming to completion and maturity.
The part of English that reflects the real meaning of it maybe the perfect 'tense' in grammar, where something that has been happening has come to completion.
Greek Strongs numbers: G5048:
τελειόω
teleioō
tel-i-o'-o
From G5046; to complete, that is, (literally) accomplish, or (figuratively) consummate (in character): - consecrate, finish, fulfil, (make) perfect.
and G5056:
τέλειος
teleios
tel'-i-os
From G5056; complete (in various applications of labor, growth, mental and moral character, etc.); neuter (as noun, with G3588) completeness: - of full age, man, perfect.
So this isn't about sinlessness.. but maturity.
David was considered as mature in His faith.. a great faithful man in Christ.. but he struggled with temptation.
Paul was a great mature man of faith but he wasn't perfect in the sinless sense. This applies to all the great biblical characters aside from Jesus and His angels.
