John Gill Commentary Luke 6:34

"And if ye lend to them of whom ye hope to receive, what thank have ye? even sinners lend to sinners, to receive again as much." — Luke 6:34 (ASV)

And if you lend to them of whom you hope to receive
The same again, as from their brethren the Jews; or usury, as from the Gentiles:

what thank do you have ?
and yet they looked upon this, in the first instance of it, as a very great kindness, and act of goodness, as appears from the above citation:

for sinners also lend to sinners, to receive as much again ;
or "what is equal", and answerable to what they have lent them; that is, the same, or what is equivalent to it.