Authorities believe the suspect is a homeless man who appears to be in his 50s.
According to police, he was harassing people on a southbound D train that was pulling into the 47th-50th Streets-Rockefeller Center station.
Investigators said the 27-year-old victim intervened, their verbal dispute turned physical, and the suspect pulled out a pocket knife.
He stabbed the victim in the stomach before fleeing the train and the station.
The victim was taken to NewYork-Presbyterian/Weill Cornell Medical Center for treatment.
Anyone with information is asked to call the NYPD's Crime Stoppers Hotline at 1-800-577-TIPS.
EXCLUSIVE | Bronx apartment residents say they are being terrorized, beaten by teens who come to building
Apartment residents say they are being terrorized, beaten by teens
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