In Luke 15:20, for this boy's father to have seen him "a great way off" would imply that the Father had been eagerly awaiting his son's return. In the spiritual application of this parable, our Heavenly Father is longing to cleanse and receive the sinner, if he will just repent and come to Him for forgiveness.

Jesus was using this parable to rebuke the Pharisees for their harsh, self-righteous, unforgiving attitude towards sinners. 

The older brother in this parable was symbolic of the Pharisees. Like this brother, the Pharisees had not lived an outward life of rebellion and they thought that others who didn't measure up to their standards were surely hated by God. But, "God so loved the world" and "Christ Jesus came into the world to save sinners."

Just as this older brother was self-centered and jealous, the Pharisees were not operating in the love of God towards sinners because they were so in love with themselves. They resented Jesus giving the sinners what the Pharisees thought they deserved.

If relationship with his father had been the real desire of the older brother, he would have rejoiced to see his father's joy at the return of his son. The repentant prodigal son had learned the vanity of things and he had come home to a relationship with his father that neither he nor his older brother had known before.

The scribes and Pharisees, like the older brother, had gotten caught up in serving self through their religious actions. The publicans and sinners who repented were supplying their Father with what He really wanted - relationship.

Relationship with the Father was always available to the scribes and Pharisees, but they chose the temporal praise of men rather than relationship with God.