When Saad was buried and we were with the Messenger of Allah ﷺ, the Messenger of Allah ﷺ said "Subhan Allah," and the people said it along with him for a long time. Then he said "Allahu Akbar," and the people said it with him.They asked, "Messenger of Allah, why did you say 'Subhan Allah'?"He replied, "The grave pressed in upon this righteous man until Allah relieved him of it."
حدثنا يعقوب حدثنا أبي عن ابن إسحاق حدثني معاذ بن رفاعة عن محمود بن عبد الرحمن بن عمرو بن الجموح
لما دفن سعد ونحن مع رسول الله ﷺ سبح رسول الله ﷺ فسبح الناس معه طويلا ثم كبر فكبر الناس ثم قالوا يا رسول الله مم سبحت قال لقد تضايق على هذا الرجل الصالح قبره حتى فرجه الله عز وجل عنه
No references are available.
Its isnad is sahih, and it has already appeared at 1809.