Sayyiduna Uthmaan Radhiyallahu Anhu advices on the Grave

Whenever Sayyiduna Uthmaan رَضِيَ اللهُ عَنْهُ stood by a grave he would weep until his beard was soaked.
He was asked, “Paradise and Hell are mentioned, yet you do not weep; why do you weep at this?” He replied, سيدنا Rasulullah ﷺ said: ‘The grave is the first stage of the Hereafter; if one is saved from it, what follows is easier, but if one is not saved from it, what follows is more severe.’ He added that the Messenger of Allah ﷺ also said: ‘I have never seen a sight more terrifying than the grave.'”
Ibn Majah

Sayyiduna Uthmaan رَضِيَ اللهُ عَنْهُ said that when سيدنا Rasulullah ﷺ finished the burial of the dead he stood over it and said, “Ask forgiveness for your brother, then ask that he may be strengthened, for he is now being questioned.”
Abu Dawud