I heard the Messenger of Allah ﷺ say, "When one of you prays and then remains seated in his place of prayer, the angels keep saying, 'Allah, forgive him. Allah, have mercy on him,' as long as he does not break his ablution or get up."
حدثنا يعلى حدثنا محمد بن إسحاق عن العلاء بن عبد الرحمن عن أبيه
سمعت رسول الله ﷺ يقول إذا صلى أحدكم ثم جلس في مصلاه لم تزل الملائكة تقول اللهم اغفر له اللهم ارحمه ما لم يحدث أو يقوم
Its isnad is sahih. Malik also related it in the Muwatta, p. 160, with similar wording, from Abu Zinad, from Aaraj, from Abu Hurairah. Bukhari likewise related it, 1:448 and 2:119, by way of Malik, and Muslim related it, 1:184, through several routes. Its meaning has already passed at 7424, within a lengthy hadith narrated by Amash from Abu Salih, from Abu Hurairah, and we cited it there also from the Sahihayn. Its meaning has also already passed, from the hadith of Ali bin Abu Talib, at 1218 and 1250.As for his saying "or he stands," it is thus established in the three original manuscripts, with the waw retained despite its being conjoined to a jussive word. This is permissible, and it has its justification in Arabic grammar.