Athanasius the Great
Catena Aurea · Lukasevangelium 12
Also I say unto you, Whosoever shall confess me before men, him shall the Son of man also confess before the angels of God: But he that denieth me before men shall be denied before the angels of God. And whosoever shall speak a word against the Son of man, it shall be forgiven him: but unto him that blasphemeth against the Holy Ghost it shall not be forgiven. And when they bring you unto the synagogues, and unto magistrates, and powers, take ye no thought how or what thing ye shall answer, or what ye shall say: For the Holy Ghost shall teach you in the same hour what ye ought to say.
(Ep. 4. ad Serap.) The ancients indeed, the learned Origen and the great Theognostus, describe this to be the blasphemy against the Holy Ghost, when they who have been counted worthy of the gift of the Holy Spirit in Baptism, fall back into sin. For they say that for this reason they can not obtain pardon; as Paul says, It is impossible for those who have been made partakers of the Holy Ghost to renew them again, &c. (Heb. 6:4.)