This article is from the The Osbourne FAQ, by Mike L. with numerous contributions by others.
By now, all four members of the band were staying in their rooms all day
and doing hard drugs and booze. They had cars, success, and perhaps little
motivation to release another album. Ozzy himself has said he only wanted
to release an album to make money and get fat off of beer. Ozzy would
subsequently not show up for weeks at a time for practice. They were to
begin work on their next album, "Heaven and Hell". Tony, having met Ronnie
James Dio (ex-Rainbow) by this time, then asked Bill to get rid of Ozzy.
Tony was fed up with Ozzy and was interested in having Dio as a vocalist.
After the 1978 NSD tour, Ozzy was told by Bill, that they no longer wanted
him in the band. Bill feels bad about doing this because him and Oz were
best of friends and yet Bill wanted Ozzy out of the band as well. People
still ask how Ozzy left, the truth is that both him and Tony Iommi say he
was fired. Ozzy also adds that he was relieved at this. In actual fact Ozzy
was asked many times on the last day to leave before being fired. For some
time now Ozzy wanted to go into a new musical direction and perhaps was
unable to do so with the politics of the band being the way they were.
Tony, being the transportation, would never be spoken against by the other
members of the band. 1978 saw the end of the original Black Sabbath. Their
last tour would be the "Never Say Die" tour. Appropriately named.