The article talks about the actions of God as described by prophet Hosea in Hos 2: 16-25, which are the consequence of the sin and the unfaithfulness shown by Israel to God. Despite the fact that Israel's sin of should be met with punishment from God, Hosea predicts God's mercy. To formulate this, the prophet applies a rare idiomatic Hebrew expression על־לב דבר, which could be translated as talking kindly to the heart. The article conducts a short analysis of nine instances in the Bible in which this expression has been used, underlining the difficulties and lack of consequences in translating this expression to Polish. Subsequently, an interpretation of על־לב דבר, as applied by Hosea in the above mentioned passage, was carried out. The explanation of the idiom has as its aim a more profound understanding of the message conveyed in the selected excerpt. The use of the image of marriage in this text, which is accompanied by forgiveness to an unfaithful wife, became for Hosea an illustration of mercy that God shows to His believers.