In Matt 16:17, Jesus tells Peter that it was not "flesh and blood" (σαρξ και αιμα) that revealed Jesus' identity to Peter. Such is a common term in Jewish sources depicting human frailty and dependence on God. Note the following from B. Berakhot 28b, for instance:
He said to them: I cry in fear of heavenly
judgment, as the judgment of the heavenly court is unlike the judgment of man. If
they were leading me before a flesh and blood king whose life is temporal, who
is here today and dead in the grave tomorrow; if he is angry with me,
his anger is not eternal and, consequently, his punishment is not eternal; if
he incarcerates me, his incarceration is not an eternal incarceration, as I
might maintain my hope that I would ultimately be freed. If he kills me, his
killing is not for eternity, as there is life after any death that he might
decree. Moreover, I am able to appease him with words and even bribe
him with money, and even so I would cry when standing before royal
judgment. Now that they are leading me before the supreme King of Kings, the
Holy One, Blessed be He, Who lives and endures forever and all time; if He is
angry with me, His anger is eternal; if He incarcerates me, His incarceration
is an eternal incarceration; and if He kills me, His killing is for eternity. I
am unable to appease Him with words and bribe him with money. Moreover, but I
have two paths before me, one of the Garden of Eden and one of Gehenna, and I
do not know on which they are leading me; and will I not cry? His students said
to him: Our teacher, bless us. He said to them: May it be His will that
the fear of Heaven shall be upon you like the fear of flesh and blood. His
students were puzzled and said: To that point and not beyond?
Shouldn’t one fear God more? He said to them: Would that a person
achieve that level of fear. Know that when one commits a transgression, he
says to himself: I hope that no man will see me. If one is as
concerned about avoiding shame before God as he is before man, he will never
sin. (source)
