The following story is related in Sefer Chemdah Genuzah (Chelek 2, page 125):
One year before Pesach, Rav Yechzekel of Kuzmir zy”a sent out a man to raise funds for his mosdos. The collector came to the home of a certain wealthy man while the man was busy baking matzohs, and he totally ignored the meshulach. When the collector returned to the Rebbe, Rav Yechezkel asked if he had been to see that specific wealthy man. He answered that he had arrived at his home at a bad time because the man was busy with his matzohs when he got there.
This wealthy man came to Kuzmir for Pesach and the Rebbe gave him mussar in a veiled way. He quoted the verse that says that Yaakov struggled with a man until morning. Rashi says that this man was the angel of Esav. On the later verse (37:15) that says that Yosef met a man who asked him what he was looking for, Rashi says that this man was Malach Gavriel. He asked how Rashi knew that the “man” Yaakov encountered was the Sar of Esav, but the man Yosef met was Malach Gavriel?
He answered that Rashi tells us that when Yaakov asked the man for assistance in carrying his load, the man said that it was his time to say shira and he could not help him because he was busy with that mitzvah. That’s how we know that this was the Sar of Esav – because if a Jew needs help, this should override any other mitzvah. However, the man whom Yosef met, saw that he was wandering in the fields and asked how he could help. This proved that he was Gavriel.
