John Gill Commentary Luke 3:7

"He said therefore to the multitudes that went out to be baptized of him, Ye offspring of vipers, who warned you to flee from the wrath to come?" — Luke 3:7 (ASV)

Then said he to the multitude
That is, John, as the Ethiopic version reads; and the multitude to whom he spoke the following words, were many of the Pharisees and Sadducees, as appears from (Matthew 3:7)

That came forth to be baptized of him;
who came out of their houses, towns, and cities, round about, to the place where John was; and hearing and seeing what he was about, desired to be admitted to his baptism: not that they "were baptised of him"; as the Arabic version renders it; but they came with a view of being baptized, were it thought fit and proper they should: but John refused them, saying to them,

O generation of vipers, who has warned you to flee from the wrath to
come?
(See Gill on Matthew 3:7).