Musar zu Bereschit 38:1

Bereshit Rabbah 85, 1, commenting on Genesis 38, 1, the episode introducing Yehudah's marriage, etc., quotes Rabbi Shmuel bar Nachman who interprets Jeremiah 29,11 in which G–d is on record that all His intentions are for the good of the Jewish people, even though it may not always appear thus to us. G–d also stresses that He is fully aware of our thoughts. The sale of Joseph is an example of how what appear to be plans and actions contrary to G–d's intentions are nonetheless furthering His plans. The brothers were concerned only with ridding themselves of Joseph and the danger they thought he represented to them. Joseph and Reuben, as well as Jacob, were each mourning their part in the fate that had befallen the other; Yehudah was busy choosing a wife. G–d, on the other hand, was busy paving the way for the eventual arrival of the Messiah.