God could not have us in His presence with sin upon us- could not suffer a single speck or stain of sin. The father could not have the prodigal at his table with the rags of the far country upon him. He could go forth to meet him in those rags; he could fall upon his neck and kiss him in those rags; it was the worthy and beautiful characteristic of his grace to do so. But then to seat him at his table in the rags would never do.
The grace that brought the father out to the prodigal, reigns through the righteousness which brought the prodigal in to the father. It would not have been grace had the father waited for the son to deck himself in robes of his own providing; it would not have been righteous to bring him in, in his rags. But both grace and righteousness shone forth in all their respective brightness and beauty when the father went out and fell on the prodigal's neck, but yet did not give him a seat at the table until he was clad and decked in a manner suited to that elevated and happy position.