The only goal of the game was scored by Ronald Araujo in the 24th minute after a cross from João Cancelo from a corner kick.
The absolute hero is the "blaugrana" goalkeeper Joan Garcia, who made several miraculous saves.
This is the 19th consecutive victory for Rafinja and his teammates on home soil.
Barca are the leaders with seven points more than first-place Real, who play the city derby with Atletico tonight. On the other hand, Rayo is 14th with 32 points, just four above the relegation zone.
Hansi Flick's team will play three matches against Atletico in just 10 days after the international break, one in the championship and two in the quarterfinals of the Champions League.
