The Messenger of Allah ﷺ said, "By Him in whose hand is Muhammad's soul, were it not that I would impose hardship on the believers, I would never stay behind from any expedition setting out to fight in the cause of Allah. But I do not have the means to provide them mounts, nor do they have the means to follow me, and it does not sit well with them to remain behind when I have gone."
وقال رسول الله ﷺ والذي نفس محمد في يده لولا أن أشق على المؤمنين ما قعدت خلف سرية تغزو في سبيل الله ولكن لا أجد سعة فأحملهم ولا يجدون سعة فيتبعوني ولا تطيب أنفسهم أن يقعدوا بعدي
It is sahih by virtue of the soundness of the manuscript, and it is in the individual manuscript, numbered 18. Muslim narrated it [34:7 S / 2:96 Bulaq] through the route of the manuscript, along with the following hadith 8190. Bukhari did not narrate it with this wording through the route of the manuscript, but he narrated something similar in meaning, in abbreviated form, 6:12:13 Fath, within a hadith narrated by Saeed bin Musayab, from Abu Hurairah. It has also passed at 715, with wording similar to what is here, within a lengthy hadith narrated by Abu Zura from Abu Hurairah. It has also passed with the same meaning, in slightly abbreviated wording, at 7336, from the recension of Araj, from Abu Hurairah.