NET
15 Brothers and sisters, I offer an example from everyday life: When a covenant has been ratified, even though it is only a human contract, no one can set it aside or add anything to it.
Darby
15 Brethren, (I speak according to man,) even man's confirmed covenant no one sets aside, or adds other dispositions to.
KJV
15 Brethren, I speak after the manner of men; Though [it be] but a man's covenant, yet [if it be] confirmed, no man disannulleth, or addeth thereto.