The Gunners legend scored the only goal in a tight game at the Emirates, and admits he was surprised at his success in netting the winner so soon after his arrival
The former France international came on as a second-half substitute to mark his return to the club with the only goal of the game in the 78th minute.
"I never thought I would play for Arsenal again, and I never thought I would score the winning goal tonight," the forward told ESPN after the match.
He responded modestly when told of his welcome, responding to suggestions that he returned as a hero by adding: “That wasn’t the plan. I just wanted to come and help the team everyday.”
On his trademark curled finish to put the Gunners through, he added: "With time, you know that one opportunity is very important.
"The team played well. It’s never an easy tie. They [Leeds] came to defend and the fans were frustrated sometimes, but we did the job.
"You never know when you will have a second one, if you have a second. You have to make sure you take it, and I took it well."
The 1-0 win sends Arsenal through to the fourth round of the FA Cup, where they will take on Premier League rivals Aston Villa at the Emirates Stadium.