Abul-Aswad (May Allah be pleased with him) reported:
I came to Al- Madinah, and while I was sitting beside 'Umar bin Al-Khattab, a funeral procession passed by. The people praised the deceased, and 'Umar bin Al-Khattab said: "He will certainly enter it." Then another funeral procession passed by and the people praised the deceased. 'Umar bin Al-Khattab (May Allah be pleased with him) said: "He will certainly enter it." A third funeral procession passed by and the people spoke ill of the deceased. He said: "He will certainly enter it." I (Abul-Aswad) asked: "O Amir Al-Mu'minin (i.e., Leader of the Believers)! What do you mean by 'He will certainly enter it'?" He replied: "I said the same as was said by the Prophet ﷺ. He ﷺ said, 'If four persons testify the righteousness of a Muslim, Allah will grant him Jannah.' We asked: 'If three persons testify his righteousness?' He ﷺ replied, 'Even three'. Then we asked: 'If two?' He ﷺ replied, 'Even two.' We did not ask him (regarding the testimony) of one."

[Al-Bukhari].

وعن أبي الأسود قال: قدمت المدينة، فجلست إلي عمر بن الخطاب رضي الله عنه فمرت بهم جنازة، فأثني علي صاحبها خيراً فقال عمر: وجبت، ثم مر بأخرى، فأثني علي صاحبها خيراً، فقال عمر: وجبت، ثم مر بالثالثة، فأثني علي صاحبها شراً، فقال عمر: وجبت: قال أبو الأسود: فقلت: وما وجبت يا أمير المؤمنين؟ قال: قلت كما قال النبي ﷺى الله عليه وسلم الله عليه وسلم : “أيما مسلم شهد له أربعة بخير، أدخله الله الجنة: فقلنا: وثلاثة؟ قال: “وثلاثة" فقلنا: واثنان؟ قال: "واثنان" ثم لم نسأله عن الواحد" ((رواه البخاري)).