Matthew 7:3

Otherwise; The sin against the Holy Spirit is to take from God power which has influences, and from Christ substance which is of eternity, through whom as God came to man, so shall man likewise come to God. As much greater then as is the beam than the mote, so much greater is the sin against the Holy Spirit than all other sins. As when unbelievers object to others carnal sins, and secrete in themselves the burden of that sin, to wit, that they trust not the promises of God, their minds being blinded as their eye might be by a beam.

"Why beholdest thou the mote that is in thy brother's eye?" Yea, for many now do this; if they see but a monk wearing an unnecessary garment, they produce against him the law of our Lord, while they themselves are extorting without end, and defrauding men every day. If they see him but partaking rather largely of food, they become bitter accusers, while they themselves are daily drinking to excess and surfeiting: not knowing, that besides their own sins, they do hereby gather up for themselves a greater flame, and deprive themselves of every plea. For on this point, that thine own doings must be strictly inquired into, thou thyself hast first made the law, by thus sentencing those of thy neighbor. Account it not then to be a grievous thing, if thou art also thyself to undergo the same kind of trial.

He speaks of such as though themselves guilty of mortal sin, do not forgive a trivial fault in their brother.

(Serm. in Mont. ii. 18.) The Lord having admonished us concerning hasty and unjust judgment; and because that they are most given to rash judgment, who judge concerning things uncertain; and they most readily find fault, who love rather to speak evil and to condemn than to cure and to correct; a fault that springs either from pride or jealousy—therefore He subjoins, Why seest thou the mote in thy brother's eye, and seest not the beam in thy own eye? (ubi sup.) As if he perhaps have sinned in anger, and you correct him with settled hate. For as great as is the difference between a beam and a mote, so great is the difference between anger and hatred. For hatred is anger become inveterate. It may be if you are angry with a man that you would have him amend, not so if you hate him.

Otherwise; This is spoken to the doctors. For every sin is either a great or a small sin according to the character of the sinner. If he is a laie, it is small and a mote in comparison of the sin of a priest, which is the beam.