Cardi B, 26, said she was even rehearsing a new move she planned to incorporate into the show. The tweet included a video -- which was also posted to Instagram -- showing soundcheck preparations for the show, the Indianapolis Star reported.
Officials with Bankers Life Fieldhouse said the show was rescheduled for Sept. 11, WXIN reported.
In a statement, arena officials cited "circumstances beyond anyone's control" for the postponement, the Star reported.
The concert's promoter, Mammoth Live, said in a statement that "Due to a security threat and safety concerns at this evening's show, management has advised that this show be postponed. These threats are currently under investigation."
Saweetie and supporting act Kevin Gates were scheduled to take the stage between 7 and 9 p.m., with Cardi B to follow, the Star reported.
Cardi B has had three No. 1 hits on the Billboard Hot 100. She won a Grammy Award for best rap album of the year with her 2018 release, "Invasion of Privacy."