'Custom' in the Bible

So the servants served Joseph by himself [in honor of his rank], and his brothers by themselves, and the Egyptians who ate with him by themselves, because [according to custom] the Egyptians could not eat food with the Hebrews, for that is loathsome to the Egyptians.

When they came to the threshing floor of Atad, which is beyond the Jordan, they mourned there with a great lamentation (expressions of mourning for the deceased) and [extreme demonstrations of] sorrow [according to Egyptian custom]; and Joseph observed a seven-day mourning for his father.