Sa’īd b. Jubayr – Allāh have mercy on him – reports that a man once asked Ibn ‘Abbās – Allāh be pleased with them:
“How many kabā`ir (major, deadly sins) are there? Seven?” He replied, “They are closer to seven hundred than seven; except a major sin does not remain so if one (truly) seeks forgiveness [from Allāh], and a lesser sin does not remain so if one insists on continuously doing it (i.e. it becomes a major sin).”
Al-Tabarī, Al-Tafsīr article 9207, et al.