It is narrated from Hazrat Abu Huraira (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him) said: When a person commits adultery, he is not a believer at that moment; when a person steals, he is not a believer at that moment; when a person drinks alcohol, he is not a believer at that moment. And the door of repentance is open.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 10216