A.T. Robertson Commentary Matthew 20:4

"and to them he said, Go ye also into the vineyard, and whatsoever is right I will give you. And they went their way." — Matthew 20:4 (ASV)

Whatsoever is right (ο εαν η δικαιον). "Is fair" (Allen), not anything he pleased, but a just proportionate wage. Indefinite relative with subjunctive εαν=αν.