Smart's shove came with about 11 minutes remaining in the third frame of Boston's 118-115 setback Wednesday at the Wells Fargo Center in Philadelphia. The Celtics led 69-58 when Sixers guard Ben Simmons held the ball out near half-court during an offensive possession for Philadelphia.
Smart was guarding J.J. Redick when Embiid stepped up and picked him in the paint. The hard pick sent Smart to the floor. He quickly got to his feet and shoved Embiid, who was walking away from the play. Embiid also fell to the floor, before getting up and going after Smart.
Embiid and Smart were separated and Smart was given a flagrant foul and ejected.
"Obviously I was frustrated because it was a cheap shot I didn't see coming," Embiid told reporters. "It caught me off-guard."
Embiid said he was motivated by the altercation.
The Sixers big man had a game-high 37 points and a career-high 22 rebounds in the win. Smart had three points and four assists in 19 minutes of action for Boston. Kyrie Irving led the Celtics with 36 points. Irving also had nine rebounds and four assists in the loss.