Barcelona re-established their eight-point lead at the top of La Liga thanks to a routine win over struggling Cadiz.
Sergi Roberto gave Barca the lead late in the first half from a rebound after Robert Lewandowski had a header cleared off the line.
Three minutes later Lewandowski drilled in a fine drive from the edge of the box after being picked out by Roberto.
It was both players’ first league goal at the Nou Camp since 23 October’s 4-0 win over Athletic Bilbao.
Xavi’s side had chances to increase their lead further with Lewandowski hitting the crossbar.
The Poland striker has scored 15 goals in his first 19 La Liga appearances – with only Cristiano Ronaldo, in 17 games in 2009-10, reaching that total in fewer matches since the turn of the century.
Barcelona, whose nearest title rivals Real Madrid beat Osasuna 2-0 on Saturday, have won their past seven La Liga games and are unbeaten in 13.