For whosoever shall do the will of my Father who is in heaven. When he says that they do the will of his Father, he does not mean that they fulfill, in a perfect manner, the whole righteousness of the law; for in that sense the name brother, which is here given by him to his disciples, would not apply to any man. But his design is, to bestow the highest commendation on faith, which is the source and origin of holy obedience, and at the same time covers the defects and sins of the flesh, that they may not be imputed. This, says Christ in a well-known passage, is the will of my Father, that whosoever seeth the Son, and believeth in him, may not perish, but have eternal life, (John 6:40.) Although these words seem to imply that Christ has no regard to the ties of blood, yet we know that in reality he paid the strictest attention to human order, and discharged his lawful duties towards relatives; but points out that, in comparison of spiritual relationship, no regard, or very little, is due to the relationship of the flesh. Let us therefore attend to this comparison, so as to perform all that nature can justly claim, and, at the same time, not to be too strongly attached to flesh and blood. Again, as Christ bestows on the disciples of his Gospel the inestimable honor of being reckoned as his brethren, we must be held guilty of the basest ingratitude, if we do not disregard all the desires of the flesh, and direct every effort towards this object.

Whosoever shall do the will of my Father, etc. - Those are the best acknowledged relatives of Christ who are united to him by spiritual ties, and who are become one with him by the indwelling of his Spirit. We generally suppose that Christ's relatives must have shared much of his affectionate attention; and doubtless they did: but here we find that whosoever does the will of God is equally esteemed by Christ, as his brother, sister, or even his virgin mother. What an encouragement for fervent attachment to God!
1. From various facts related in this chapter, we see the nature and design of the revelation of God, and of all the ordinances and precepts contained in it - they are all calculated to do man good: to improve his understanding, to soften and change his nature, that he may love his neighbor as himself. That religion that does not inculcate and produce humanity never came from heaven.
2. We have already seen what the sin against the Holy Ghost is: no soul that fears God can commit it: perhaps it would be impossible for any but Jews to be guilty of it, and they only in the circumstances mentioned in the text; and in such circumstances, it is impossible that any person should now be found.

For whosoever shall do the will of my Father,.... This is not to be understood of a perfect obedience to the will of God, revealed in his righteous law; for since this cannot be performed by any mere man, no one could be in such a spiritual relation to Christ: but of the obedience of faith to the will of God, revealed in the Gospel; which is to believe in Christ, and have everlasting life; see John 6:40. This is the will of Christ's Father,
which is in heaven, and which is good news from heaven, to sinners on earth; and which Christ came down from heaven to do, and to declare to the children of men: such as "hear the word of God and do it", as Luke says, Luke 8:21 that is, hear the Gospel, understand and believe it, and become obedient to the faith of it; these are in this near manner related to Christ, evidentially and openly, as well as those who were now present:
the same is my brother, and sister, and mother; as dear to me, as such are to those, to whom they stood thus related in the flesh: and these natural relations serve to convey some ideas of that relation, union, nearness, and communion, there are between Christ and his people; all these relative characters may be observed in the book of Solomon's Song, to which our Lord may be reasonably thought to have respect; see Song 3:11.

For whosoever shall do the will of my Father which is in heaven, the same is my brother, and sister, and mother--that is, "There stand here the members of a family transcending and surviving this of earth: Filial subjection to the will of My Father in heaven is the indissoluble bond of union between Me and all its members; and whosoever enters this hallowed circle becomes to Me brother, and sister, and mother!"

The same is my brother. Not those with fleshly ties, but those who do the will of his Father in heaven. Such become God's spiritual children, and thus become spiritually related to the Son of God. It will be observed that there is no hint of adoration of Mary, his mother, here, or elsewhere in the Scriptures. That she was immaculately born, as the "Queen of Heaven" and the "Mother of God," is a Catholic fable.