Commentaries:
Robertson's Word Pictures (NT)
These which hear the word of God and do it (oi ton logon tou qeou akouontev kai poiountev). The absence of the article with "mother" and "brothers" probably means, as Plummer argues, "Mother to me and brothers to me are those who etc." No one is a child of God because of human parentage (John 1:13). "Family ties are at best temporal; spiritual ties are eternal" (Plummer) . Note the use of "hear and do" together here as in Matthew 7:24; Luke 6:47 at the close of the Sermon on the Mount. The parable of the sower is almost like a footnote to that sermon. Later Jesus will make "doing" a test of friendship for him (John 15:14).
Other Robertson's Word Pictures (NT) entries containing Luke 8:21:
Luke 8:11
John 7:5
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