Jesus has already preached (sown) for a considerable time. He was met by two reactions: faith and unbelief. This now leads him to speak in a way that makes this division visible. And the parable that fits this discourse is that of the sower: if you do not want to hear the word (receive it as in good soil), you will lose it!1
1 Again he began to teach beside the sea. And a very large crowd gathered about him, so that he got into a boat and sat in it on the sea, and the whole crowd was beside the sea on the land.