Abu Bakrah Nufai' bin Al-Harith (May Allah be pleased with him) reported:
Messenger of Allah ﷺ said, "Shall I not inform you of the biggest of the major sins?" Messenger of Allah ﷺ asked this question thrice. We said, "Yes, O Messenger of Allah. (Please inform us.)". He said, "Ascribing partners to Allah, and to be undutiful to your parents". Messenger of Allah ﷺ sat up from his reclining position and said, "And I warn you against giving forged statement and a false testimony; I warn you against giving forged statement and a false testimony". Messenger of Allah ﷺ kept on repeating that warning till we wished he would stop.

[Al-Bukhari and Muslim].

و عن أبي بكرة نفيع بن الحارث رضي الله عنه قال: قال رسول الله ﷺ: "ألا أنبئكم بأكبر الكبائر؟" -ثلاثًا- قلنا: بلى يا رسول الله: قال: "الإشراك بالله، وعقوق الوالدين، وقتل النفس، واليمين الغموس" ((رواه البخاري)).