Rajabov was competing with Chinese rival Ding Liren. Rajabov gained a victory on the 46th move.
As a result, the Azerbaijani representative equalized the total score - 1.5: 1.5. The finalists will hold their last matches on Oct. 3.
In case of a tie, a tie-break will take place on October 4.
Some 128 chess players are competing in the tournament. The prize fund is $1.6 million. The winner will receive $110,000.
The victory also gives the winner the right to compete for the chess crown with current world champion Norwegian Magnus Carlsen.