Whenever Uthman bin Affan stood by a grave, he would weep until his beard was soaked. Someone said to him, "You remember Paradise and the Fire and do not weep, yet you weep at this?"He replied, "The Messenger of Allah ﷺ said, 'The grave is the first stage of the Hereafter. Whoever is saved from it, what comes after will be easier, and whoever is not saved from it, what comes after will be more severe.'"He continued, "The Messenger of Allah ﷺ also said, 'I have never seen any sight more terrifying than the grave.'"
حدثنا محمد بن إسحق حدثني يحيى بن معين حدثنا هشام بن يوسف عن عبد الله بن بحير
كان عثمان بن عفان إذا وقف على قبر يبكي حتى يبل لحيته فقيل له تذكر الجنة والنار ولا تبكي وتبكي من هذا قال إن رسول الله ﷺ قال إن القبر أول منازل الآخرة فإن نجا منه فما بعده أيسر منه وإن لم ينج منه فما بعده أشد منه قال وقال رسول الله ﷺ ما رأيت منظرا قط إلا والقبر أفظع منه
[Its chain of transmission is hasan]. Tirmidhi collected it in the Book of Zuhd, Chapter on What Has Been Related About the Horror of the Grave and That It Is the First of the Stages of the Hereafter, no. 2308, from the hadith of Yahya bin Main, and he said, hasan gharib.