What is the meaning and ruling of testifying to the goodness of the deceased?

Testifying to the goodness of a deceased person, meaning that Muslims bear witness that the person was a good believer, is called "tezkiye." Every Muslim should strive to live a life that will earn them a good testimony after their death. It is also hoped that the deceased will benefit from the positive testimonies of those who knew them. The Prophet Muhammad (peace be upon him) said: “When a Muslim dies and four households from his close neighbors testify, ‘We know nothing but good about this person,’ Allah the Almighty says: ‘O believers! I have accepted your testimony about this deceased, and I have forgiven the faults you do not know.’” (Ahmed b. Hanbel, al-Musnad, 3/242 [13565])

For tezkiye, before or after the funeral prayer, when asked, “How did you know this person?” it is appropriate to testify “We knew him/her as good” for those known to be good, to remain silent for those known to be bad, and to say “May Allah have mercy on them” for those who are not known. For the Prophet Muhammad (peace be upon him) said: “Mention the good deeds of your deceased and do not speak of their bad deeds.” (Abu Dawud, Adab, 49 [4900]; Tirmidhi, Janaiz, 34 [1019])

Source: T.C. Diyanet İşleri Başkanlığı, Din İşleri Yüksek Kurulu