From the book HaYom Yom for Tuesday, 17 Nisan - 2nd day of the Omer:

"Whoever expands on the narrative of the exodus from Egypt, this person (Harei Zeh) is to be praised" (Passover Haggada).

The Hebrew word Zeh ("this") indicates a state of holiness, as in the phrase, "Here, this (zeh) is our G-d". Whoever expands on the narrative of the exodus, "his Zeh", his element of holiness, is enriched.

This book, HaYom Yom, from Day to Day, that I often quote from has now returned to print. Find it here.