(21) My mother and my brethren.—The answer agrees very closely with that in the other Gospels. But note the use of “the word of God,” instead of “the will of God” in St. Mark, and “the will of my Father” in St. Matthew, as throwing light on the meaning of the former phrase, and showing its fulness and width of meaning.

8:4-21 There are many very needful and excellent rules and cautions for hearing the word, in the parable of the sower, and the application of it. Happy are we, and for ever indebted to free grace, if the same thing that is a parable to others, with which they are only amused, is a plain truth to us, by which we are taught and governed. We ought to take heed of the things that will hinder our profiting by the word we hear; to take heed lest we hear carelessly and slightly, lest we entertain prejudices against the word we hear; and to take heed to our spirits after we have heard the word, lest we lose what we have gained. The gifts we have, will be continued to us or not, as we use them for the glory of God, and the good of our brethren. Nor is it enough not to hold the truth in unrighteousness; we should desire to hold forth the word of life, and to shine, giving light to all around. Great encouragement is given to those who prove themselves faithful hearers of the word, by being doers of the work. Christ owns them as his relations.See the notes at Matthew 12:46-50. Lu 8:19-21. His Mother and Brethren Desire to Speak with Him.

(See on [1600]Mt 12:46-50).

See Poole on "Luke 8:20"

And he answered and said unto them,.... Not to his mother and brethren, but to those that told him of them, who either designed to reproach him with them, by reason of the meanness of them, or to interrupt him in his work:

my mother and my brethren are these; pointing to his disciples:

which hear the word of God; which he had been preaching, and was meant by the seed in the preceding parable:

and do it; behave in their lives and conversations agreeably to it; and observe the precepts and ordinances in it; elsewhere called the will of God his Father; See Gill on Matthew 12:49. See Gill on Matthew 12:50.

And he answered and said unto them, My mother and my brethren are these which hear the word of God, and do it.