The word here translated as “mercy” comes from the Hebrew root רָחַם [rachem] that can be described as a mother’s deep love that comes from her innermost being.
In other words, God loves Jerusalem with an indescribable love. As proof of that love He promises that once again His earthly house, the Temple, will be rebuilt there. Furthermore Jerusalem will be restored to the fullness of God’s glory.
‘Therefore thus says the LORD:
“I am returning to Jerusalem with mercy;
My house shall be built in it,” says the Lord of hosts,
“And a surveyor’s line shall be stretched out over Jerusalem.”’
PRAY FOR THE DAY WHEN JERUSALEM WILL BE RESTORED AND THE TEMPLE WILL BE REBUILT.