Very good catch! It is the Tsaddi KeyWord Tsachaq (To Laugh). The Bible chapter where it appears the most is Genesis 18. It is wonderful. Sarah laughs because of the announcement that a woman of her age would become pregnant.
Isaac is a type of Christ, and the announcement of His Appearance is materialized in Matthew, on Spoke 18 of the Bible Wheel.
Isaac is born in Genesis 21, when we read that the Sarah's laughter was now one of joy. And also Ishmael "mocks" Isaac (same word tsachaq). This is the beginning of the persecution of Abraham's seed.
In John on Spoke 21 we read about a discussion on who the children of Abraham were (Chapter 8). The Jewish leaders despised Christ, showing that they were like Ishmael. And Christ mentioned the joy of Abraham in that discussion:
Joh 8:56 Your father Abraham rejoiced to see my day: and he saw it, and was glad.Abraham had a prophetic glimpse of the Advent of Christ in the person of his son Isaac, whose birth brought great joy.