“When I begrudgingly signed the Omnibus Bill, I was promised the Wall and Border Security by leadership. Would be done by end of year (NOW). It didn’t happen!"
--- President Donald Trump
https://www.nationalreview.com/news/donald-trump-wont-sign-temporary-spending-bill-over-border-wall-funding/
"I was promised the Wall and Border Security by leadership," Trump tweeted. "Would be done by end of year (NOW). It didn't happen! We foolishly fight for Border Security for other countries - but not for our beloved U.S.A. Not good!"
https://ktla.com/2018/12/20/trump-wont-sign-bill-avoiding-government-shutdown-because-it-doesnt-fully-fund-border-wall-speaker-ryan-says/
President Trump only signed the last Omnibus funding bill because it included the money he wanted for the military and because he was promised his border wall funding in the next DHS funding bill. Well, the funding is not there, so the line has been crossed and now he's forced to stand his ground.