Both the prodigal son and his brother were equally sinful. The younger son had not understood the purpose of grace, which is to grow into the maturity of holiness. But the older son had never known his father's heart. He had always sought to earn his father's love by obeying and doing. He could not accept that his dad had always loved him unconditionally, totally apart from his good works. The truth was, his father loved him simply because he was born of him.
"Therefore came his father out, and entreated him. And he answering said to his father, Lo, these many years do I serve thee, neither transgressed I at any time thy commandment: and yet thou never gavest me a kid, that I might make merry with my friends. But as soon as this thy son was come, which hath devoured thy living with harlots, thou hast killed for him the fatted calf" (Luke 15:28-30).
The older son was saying to his father, "All these years I've worked so hard to please you, yet you've never shown me this kind of love. At least I have never felt it." This sums up the root problem of the protesting son. He thought he had earned, through good works, what his younger brother had received through grace.
Every legalist has a difficult time setting aside the works of his flesh. Why? Because our flesh wants to perform for God! We want to be able to say, "I've earned my peace in the Lord. I've fasted, prayed, done everything to get the victory. I've worked hard and now I've finally made it.”
If we are honest, we will see that our flesh always protests against dependence on the Lord. We don't want to rely on His mercy and grace or acknowledge that only He can give us the power, wisdom and authority to live as overcomers.
We must be careful not to make the protest of the older brother. It is a protest of human uprightness—and it is a stench in God's nostrils!