τω 3588 T-DSM δε 1161 CONJ εργαζομενω 2038 5740 V-PNP-DSM ο 3588 T-NSM μισθος 3408 N-NSM ου 3756 PRT-N λογιζεται 3049 5736 V-PNI-3S κατα 2596 PREP χαριν 5485 N-ASF αλλα 235 CONJ κατα 2596 PREP το 3588 T-ASN οφειλημα 3783 N-ASN
Vincent's NT Word Studies
4. The reward (o misqov). See on 2 Pet. ii. 13.Not of grace but of debt (ou kata carin alla kata ofeilhma). Lit., according to grace, etc. Not grace but debt is the regulative standard according to which his compensation is awarded. The workman for hire represents the legal method of salvation; he who does not work for hire, the gospel method; wages cannot be tendered as a gift. Grace is out of the question when wages is in question.
Robertson's NT Word Studies
4:4 {But as of debt} (alla kata ofeilema). An illustration of the workman (ergazomen"i) who gets his wages due him, "not as of grace" (ou kata carin).