John Gill Commentary 1 Kings 15:21

"And it came to pass, when Baasha heard thereof, that he left off building Ramah, and dwelt in Tirzah." — 1 Kings 15:21 (ASV)

And it came to pass, when Baasha heard thereof
What was doing in the northern part of his kingdom:

that he left off building of Ramah ;
which was the thing designed to be answered by this diversion:

and dwelt in Tirzah ;
in the tribe of Manasseh, nearer at hand, to observe and stop the motions of the Syrian king.