From Levi Yitzhak of Berditchev, Kedushas Levi, Parshat Vayetzei.
וַיֵּצֵא יַעֲקֹב מִבְּאֵר שָׁבַע Jacob went out from Beer Sheva… Genesis 28:10
יעקב הוא מנין שבע פעמים הוי’’ה, והיה יכול לילך לחוץ לארץ לעלות ניצוצות, ויצחק הוא מנין ח’ פעמים הוי’’ה, ושם הוא למעלה מעליות ניצוצות, לכך לא הורשה לילך לחוץ לארץ
The numerical value of Jacob is seven times that of the Name of God, YHVH, so he was able to go out of the holy land to raise sparks [of divinity]. The value of Isaac is eight times that of YHVH; he is therefore above raising the sparks, and so he was not permitted to go out of the holy land.
Every Hebrew letter is also a number, and one of the most ancient mystical techniques of reading Torah (or any other word) is to find the numerical value of a word and look for meaning in that number, either in itself or by comparing it to other word-values. Here the Kedushas Levi combines this technique, called gematria, with clues in the verse to teach a deep and very Hasidic lesson on serving God. Beer means “well,” as in a well of water, and is one of the symbolic names for God; Sheva means seven. So we can read the verse, Jacob went out from God sevenfold, a reading reinforced by the fact that Jacob’s name, יעקב, is seven times the value of YHVH, י–ה–ו–ה. Seven is the number of completion in the natural world, as seen in the seven days of the week, culminating in Shabbat, the seventh day, when God “completed the heavens and the earth.” So Jacob’s task was to complete God’s creation by raising up the holy sparks scattered throughout this material world and returning them to their Source. In this way he was like his grandfather Abraham, who also was sent out of the holy land, to Egypt, to collect the holy sparks there (the “silver and gold” of Genesis 13). His father Isaac, however, was a different sort of man, so immersed in holiness that he was above the world and therefore unable to extract the divinity from it by engaging with it, in the way that Jacob could. Thus God told him not to leave the holy land (Genesis 26). We can see this in the fact that יצחק is eight times YHVH, and eight represents surpassing this world and going “beyond nature” to the realms above.
While Hasidism recognizes the value of holy people like Isaac, it realizes that for most of us this is not the best way to serve God. For us the model is Jacob, who (after much trial and error, as we see in this and the next parshah) combined and perfected the ways of his father and grandfather, learning to leave the security of the tents behind (“Jacob was a meek man, staying in the tent” — Genesis 25:27) and venture out into the world in pursuit of holiness there. So, though we may be working on a “lower level” of “seven” instead of “eight,” we can do all the more holy work.