I originally gave this Dvar Torah at the Teaneck Carlebach Minyan for parshat Vayishlach. So this may be said either on Shavuot due to its content or on Vayishlach where the passuk and the Rashi are found.
Im Lavan garti
Rashi: V'taryag mitzvot Shamarti
Q: Was Ya'akov Avinu a kohen gadol? A Yabbam? How could he possibly have observed 613 Mitzvos?
A: (bekitzur). Ya'akov-Yisroel was the last of the avos the last to be "kolel" the entire nation. I.E. he included every one of the eventual am Yisroel. Once the shevatim separated, levi'i'm and kohanim had separate mitzvos from others. There would never again be one individual who would encompass all 613.
This point was most applicable to Ya'akov Avinu: That he keep all 613 mitzvos. No other individual could ever do this again.