What does Genesis 31:21 mean?

For some two decades, Jacob has been abused and cheated by Laban. This began with a jaw-dropping betrayal, tricking Jacob into marrying Leah, and coercing him into working a second stint of seven years as a result (Genesis 29:20–28). It continued with Laban's repeated efforts to take advantage of Jacob, including unfair tactics (Genesis 30:31–36), and an attempt to change their agreement several times (Genesis 31:4–13). Even Laban's feuding daughters (Genesis 30:8), now the wives of Jacob, recognized that their father was a dishonest, greedy man who held no real love for them (Genesis 31:14–16). So, with the blessing of his wives, Jacob has pushed his caravan of family, camels, donkeys, servants, belongings, and livestock as quickly as he could. He wanted to put real distance between himself and Laban before his father-in-law realized he was gone.

Jacob's strategy here strongly implies that Laban wouldn't have voluntarily allowed them to leave. In fact, based on Laban's own words later on, Jacob might have had reason to fear violence (Genesis 31:29).

By waiting until Laban was a few days away, shearing his own flock (Genesis 31:19), Jacob achieved some distance, reaching and crossing the Euphrates River and heading toward Gilead. It would not be enough, however, to keep Laban from catching up to him.