John Calvin Commentary Luke 15:28

"But he was angry, and would not go in: and his father came out, and entreated him." — Luke 15:28 (ASV)

Therefore his father went out. By these words, he reproaches hypocrites with intolerable pride, which makes it necessary that the Father should entreat them not to envy the compassion shown to their brothers. Now, though God does not entreat, yet by his example he exhorts us to bear with the faults of our brothers.

And to take away every excuse from wicked severity, he not only introduces hypocrites as speaking, whose false boasting might be refuted, but even affirms that, though any man had fulfilled, in the most perfect manner, all the duties of piety towards the Father, yet he has no just reason to complain because his brother obtains pardon.

It is certain, indeed, that the sincere worshippers of God are always pure and free from this malignant disposition; but the design of Christ is to show that it would be unjust for any man to complain about his brother having been received into favor, even though he were not inferior in holiness to the angels.