How do we know that God's grace is given unconditionally?

In Matthew 20, the landowner's decision to pay all laborers the same wage illustrates God's unconditional grace. Those hired last received a denarius, the same amount as those who worked the entire day. This reflects God's sovereign choice to grant forgiveness and salvation to anyone He calls, irrespective of their past actions or the timing of their conversion. The narrative emphasizes that God's gifts are not a reward for labor but a manifestation of His generosity and love. This doctrine challenges the self-righteous notion that one can earn favor with God through works, reaffirming that salvation is by grace alone.