Allah admits to Paradise any Muslim whose goodness is testified to by four people

A funeral procession passed by ‘Umar ibn al-Khattāb (may Allah be pleased with him) while some people were sitting with him. The people testified to the goodness and righteousness of the deceased, whereupon ‘Umar (may Allah be pleased with him) said: That is confirmed for him.

Another funeral passed by and the people testified to the goodness and righteousness of the deceased – just as they did in the first funeral – whereupon ‘Umar (may Allah be pleased with him) said: That is confirmed for him. Then a third funeral passed by and the people testified to the evil condition of the deceased, whereupon ‘Umar (may Allah be pleased with him) said: That is confirmed for him.

The statement of ‘Umar (may Allah be pleased with him) confused Abu al-Aswad, so he sought a clarification of its meaning. He,(may Allah be pleased with him) replied that he had said as the Prophet (may Allah's peace and blessings be upon him) said: Paradise is guaranteed for any Muslim whose goodness and righteousness is testified to by four people from among the good and righteous.

When the Companions heard that from the Prophet (may Allah's peace and blessings be upon him) they inquired if a person will be among the inhabitants of Paradise if three people testify to his goodness and righteousness, to which he replied in the affirmative. Then they inquired if that will be the case if only two people testify to his goodness and righteousness, to which he also replied in the affirmative.

However, they did not ask him if a person will be among the inhabitants of Paradise if only one person testifies to his goodness and righteousness.