A.T. Robertson 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)

If ye lend (εαν δανισητε). Third-class condition, first aorist active subjunctive from δανιζω (old form δανειζω) to lend for interest in a business transaction (here in active to lend and Mt 5:42 middle to borrow and nowhere else in N.T.), whereas κιχρημ (only Lu 11:5 in N.T.) means to loan as a friendly act.

To receive again as much (ινα απολαβωσιν τα ισα). Second aorist active subjunctive of απολαμβανω, old verb, to get back in full like απεχω in 6:24. Literally here, "that they may get back the equal" (principal and interest, apparently). It could mean "equivalent services." No parallel in Matthew.