A man was stabbed with a knife and socked with brass knuckles after an argument inside a Brooklyn subway station, police said Sunday.

The attacker approached an 18-year-old man about 5:55 a.m. Saturday on a subway platform inside the Broadway Junction station.

At one point, possibly before the argument, as seen in a cell phone video the victim provided to police, the attacker just stares into the teenager’s face without saying anything.

After the two argued, the stranger then stabbed the victim in the back with a knife and, for good measure, punched him in the left eye with brass knuckles. The assault left the victim with a cut on his back and bruising and swelling on his face.

The injured man went by private means to Kings County Hospital where he was in stable condition.

The attacker fled onto an uptown A train and has yet to be caught by police. It remains unclear what sparked the attack.

Cops released the cell phone footage of the suspect and are asking the public’s help identifying him and tracking him down.

Anyone with information is asked to call Crime Stoppers at (800) 577-TIPS.