The Icelandic midfielder stroked into the bottom corner two minutes from time to spark jubilant scenes at Tynecastle on Tuesday.
Hearts stretch their lead at the top of the table to six points over Rangers, who have a game in hand, and nine ahead of defending champions Celtic, who have played two fewer games than the Jambos.
Rangers face a tough trip to fourth-placed Motherwell on Wednesday before the top two face off at Ibrox this weekend.
No side outside the Old Firm duo have won the Scottish title for 41 years.
"You've got to celebrate these moments, we know how important they are. You've just got to win it some way," said Hearts boss Derek McInnes.
"We've been well convinced for a while we have a chance. It would be foolish to think with 12 games to go that we don't have a chance.
"If Celtic and Rangers don't win the league it's a disaster for them. For us we're enjoying what we're doing."