The appointed Old Testament reading for the second Sunday in Advent is Malachi 4, it offers us a rich description of the coming Messiah:
For behold, the day is coming, burning like an oven, when all the arrogant and all evildoers will be stubble. The day that is coming shall set them ablaze, says the Lord of hosts, so that it will leave them neither root nor branch. But for you who fear my name, the Sun of Righteousness shall rise with healing in its wings. You shall go out leaping like calves from the stall. And you shall tread down the wicked, for they will be ashes under the soles of your feet, on the day when I act, says the Lord of hosts
The IHC Christmon below combines both the IHC Christogram and the Sun of Righteousness symbol.
In the Latin-speaking Christianity of medieval Western Europe (and so among Catholics and many Protestants today), the most common Christogram became "IHS" or "IHC", denoting the first three letters of the Greek name of Jesus, ΙΗΣΟΥΣ, or ΙΗΣ.