Beram Kayal scored his first goal for Celtic to defeat St Johnstone and return Celtic lead at the top of the table to five points.
The home side made a lively start on the poor surface although it was Celtic who gradually began to dominate possession and the chances.
Smith could only parry a powerful, 25-yard free-kick from Commons and, when the goalkeeper punched a cross clear, Commons' first-time volley from a similar distance flew a few yards over.
Samaras then had a chance to score as he raced into the box and curled a low drive that would have found the far corner of the net but goalkeeper Smith stuck out a leg and saved the shot.
The home side were occasionally dangerous on the break and should have had a free-kick on the edge of the box when Brown hauled down Stevie May.
Joe Ledley's through ball was flicked on by Scott Brown and following a couple of deflections, Kayal picked up the ball and he directed it just past the outstretched fingers of Smith and into the far corner of the net from 12 yards to score his first goal for Celtic.
The Saints could have scored when Craig advanced towards the Celtic box and fired a 25-yard drive that goalkeeper Forster did well to punch clear one-handed.
They had already used their three substitutes, ended the game with 10 men after Millar limped off with an injury.
Samaras appeared to trip Duberry, the St Johnstone defender clearly handled the ball as he fell to the ground, but no foul or penalty was given by referee Iain Brines.
Personally I think Duberry got stuck and ended up falling and thinking he would get a freekick touched the ball.
Celtic tried to secure the points but Brown fired against the underside the crossbar and for goalkeeper Smith to flick Shaun Maloney's follow-up header off the line.
So Celtic gain another 3 points,it wasnt pretty but you need to win those to win the league.
Rangers go to Aberdeen tomorrow and will hope to keep up the pressure.