The Messenger of Allah ﷺ never grieved over anything as much as he grieved over the seventy who were killed at the Well of Maunah.
قال قرئ على سفيان سمعت عاصما قال سمعت
ما وجد رسول الله ﷺ مثل ما وجد على السبعين الذين أصيبوا ببئر معونة
Its isnad is sahih, and it refers to the hadith itself.