Musar sobre Êxodo 1:5

ויוסף היה במצרים. Rashi comments on Exodus 1,5, that this statement is to testify to the righteousness of Joseph who had tended his father's flock, and who was the same Joseph after he had become viceroy in Egypt. This teaches us to cleave to G–d with all our heart even when destitute and humiliated. Also, when one achieves great stature, one should not become arrogant but remain humble and use one's greatness to perform additional מצות.

The missing letter ו in the name of Jacob, (which is usually written defective), was added to the name ו-יוסף, on occasions such as in Exodus 1,5 (or altogether, since that name too could have been spelled defective). The "small" ו in the word שלום, Numbers 25,12, alludes to another verse in Zachariah 8, 19: והאמת והשלום אהבו "and the truth and the peace they loved." The attribute which distinguishes Jacob is אמת, truth, whereas the attribute הברית השלום is the one that distinguishes Joseph. The Zohar has already explained how the terms ברית and גוף overlap (cf. Sullam edition Lech Lecha page 134-135). We name something or somebody because we desire the name to reveal their nature. Joseph was the "revelation" of the mystical dimension of Jacob, the secret of how the covenant between G–d and man influences the ability of determining the nature of him who is about to be born.