John Gill Commentary Luke 6:49

"But he that heareth, and doeth not, is like a man that built a house upon the earth without a foundation; against which the stream brake, and straightway it fell in; and the ruin of that house was great." — Luke 6:49 (ASV)

But he that hears, and does not
Hears Christ's sayings externally, but does not obey his commands:

is like a man that without a foundation built upon the earth :
that is, without digging for a foundation, built his house upon the surface of the earth; "upon the dust of it", as the Syriac version renders it; or, "upon the sand", as Matthew says: "against which the stream did beat vehemently, and immediately it fell, and the ruin of that house was great"; (See Gill on Matthew 7:26). (See Gill on Matthew 7:27).