The Messenger of Allah ﷺ said, "True patience is at the first stroke of grief."
حدثنا محمد بن رمح أنبأنا الليث بن سعد عن يزيد بن أبي حبيب عن سعد بن سنان
قال رسول الله ﷺ إنما الصبر عند الصدمة الأولى
Its isnad is hasan. Tirmidhi narrated it in the chapter on funerals, in the section titled "What Has Been Said About Patience at the First Shock," no. 987, from the hadith of Layth, transmitted in the same way, and he said it is gharib. It is also agreed upon [by Bukhari and Muslim] from the hadith of Anas , with similar wording.