if we say we "have no sin"
Do you believe Jesus cleanses us from
all unrighteousness? If you do, then there can be no sin left in him, who was cleansed from
all sin. So, in context, no one can say they have no sin because if I witness about myself, my witness is not true. They just can't witness about themselves. It doesn't mean they have sin. They don't, not if you believe they were cleansed from
all sin.
if you believe Romans 7 contradicts 1 Peter 4, you are in error:
you have at least one of them quite wrong.
Hebrews 9:27 And as it is appointed unto men
once to die, but
after this the judgment:
Dying frees you from having to obey the law, it doesn't free you from judgement. Every man will be judged according to their works:
Revelation 20:12 And I saw
the dead, small and great, stand before God; and the books were opened: and another book was opened, which is
the book of life: and
the dead were judged out of those things which were written in the books,
according to their works.