Puzzled - Troubled - Need Help

The first shtikel Sfas Emes in this weeks parsha starts by quoting the Chazal that Yaakov made Eiruv Tchumin BUT NEVER EXPLAINS IT! He just goes off on a deep Kabbalistic foray into the world of Shabbos and Chol and angels. That is SOOOOO not like him. He always explains the medrashim that he quotes. If anybody can give me a pshat - I would be indebted.