Abu Hurairah (May Allah be pleased with him) reported:
Messenger of Allah (ﷺ) was asked about the deed which will be foremost to lead a man to Jannah. He replied, "Fear of Allah and the good conduct." Then he was asked about indulgence which will admit a man to Hell (Fire) and he answered, "The tongue and the genitals."[At- Tirmidhi].
Arabic/English book reference: Book 1, Hadith 627