John Gill Commentary Luke 8:12

"And those by the way side are they that have heard; then cometh the devil, and taketh away the word from their heart, that they may not believe and be saved." — Luke 8:12 (ASV)

Those by the wayside are they that hear
The word of God, though only by accident, and very carelessly, and without understanding what they hear:

then comes the devil ;
signified by the fowls of the air:

and takes away the word out of their hearts ,
or memories; that little of it, which is retained there, and diverts their minds from it by other objects; so that they quite forget what they have heard;

lest they believe, and be saved :
this clause is only in Luke; and with it may be compared (2 Corinthians 4:4) for with true faith in Christ the sum and substance of the word salvation is connected; and Satan being an enemy to the salvation of souls, does all he can to hinder their faith in him.