John Gill Commentary Luke 12:9

"but he that denieth me in the presence of men shall be denied in the presence of the angels of God." — Luke 12:9 (ASV)

But he that denieth me before men
That is, that continues to deny Christ, and lives and dies a denier of him; for otherwise it is possible for a person to deny Jesus to be the Son of God, or the Messiah, and afterwards confess him, as a Pagan or Jew; and through temptation, a real Christian may be left for a while, in one shape or another, to deny him and his truths, and afterwards truly repent, and at last be saved, as Peter; but they that deny Christ publicly, and persist in it,

shall be denied before the angels of God :
they will be denied by Christ as belonging to him; they will be denied admission into heaven; they will be covered with shame and confusion publicly; they will be sent into everlasting burnings, and be ever tormented with fire and brimstone, in the presence of the holy angels.