When Jesus told the parable of the prodigal son, I think he was speaking about Israel. Even in the Old Testament Israel, referring to both the Northern Kingdom and the Southern Kingdom, was called God’s son. He was their father and that image of God the Father and the 
Nation of Israel being His son is often referred to. The prodigal son took all that was given to him by the father and ran off to a far country to revel in the pleasures of the world. The son was left to make his own choices and ended up with the ravages of sin on his life. He finally came to the end of himself while eating food given to the pigs belonging to his employer. When the hold of the world was finally broken, the son repented and his first thought was his father and all that he had left behind. He wanted to come home and the father was waiting to welcome him.
Jeremiah 3:21 pictures the prodigal son, the Nation of Israel, in the mud sin eating the food given to the swine. Will they come to their senses? Will they remember their Father? Will they come home? The text says no; “A voice on the bare heights is heard, the weeping and pleading of Israel’s sons because they have perverted their way; they have forgotten the Lord their God.” They have come to the end of themselves and to the end of their sin. Craigie puts it this way; “His words conjure up the sound of lament, issuing from a nation that has at last perceived the error of its ways; having forgotten God, their paths through life have become the twisted byways of evil, away from the true source of their existence. In anguish, perceiving the error of their ways, the people turn back to God in entreaty and repentance—or such was the prophet’s desire.”[1] Unfortunately, the prophet’s desire was not realized.
Huey isn’t sure who the people are “weeping to.” He thinks the description is reminiscent of the prophets of Baal in their contest with Elijah. They moaned and screamed and cut themselves but to no avail. He writes, “It is not certain whether he was describing weeping and pleading directed toward God by a repentant people or whether they were pleading with their fertility gods to hear their prayers (cf. 1 Kgs 18:26–29).”[2] The prodigal son’s heart turned towards home and the father. But Israel’s did not. They persisted in their well-worn path to destruction and found themselves without hope in a bitter, meaningless, uncaring world. We are often like that, yet there is a heavenly Father who loves us and calls to come home. He is yearning to place the family crest on our fingers and the cloak of sonship around our shoulders. We just need to come home!
[1] Peter C. Craigie, Jeremiah 1–25, vol. 26, Word Biblical Commentary (Dallas, TX: Word, Incorporated, 1998), 64.
[2] F. B. Huey, Jeremiah, Lamentations, vol. 16, The New American Commentary (Nashville: Broadman & Holman Publishers, 1993), 78.