There's a hadith in Sunan abi Dawod here and referred to it here again:
Al-Harith b. Muslim al-Tamimi quoted his father Muslim b. al-Harith al-Tamimi as saying that the Messenger of Allah (ﷺ) told him secretly:
When you finish the sunset prayer, say: 'O Allah, protect me from Hell"
Allahumma Ajirnee Min(a) an-Naar
اللهم أجرني من النار
seven times; for if you say that and die that night, protection from it would be recorded for you; and when you finish the dawn prayer, say it in a similar way, for if you die that day, protection from it would be recorded for you.
Abu Sa'id told me that al-Harith said: The Messenger of Allah (ﷺ) said this to us secretly, so we confine it to our brethren.
Sheikh al-Albani qualified it as da'if, while ibn Bazz said it has some issues in the narrator chain, but the hadith is acceptable. Imam ibn Hajar regarded it as hassan. Further there's a version of this hadith in Musnad abi Ya'ala in which no timing was mentioned which al-Albani qualified as sahih.
And further one may find:
"The Messenger of Allah [SAW] said: 'Whoever asks Allah for Paradise three times, Paradise will say: 'O Allah, admit him to Paradise.' And whoever seeks protection from Hell three times, Hell will say: 'O Allah, protect him from the Fire.'"
(Sunan ibn Majah, Sunan an-Nasa-i, Jami' at-Tirmidhi)
Which was qualified as sahih by many authorities.
See also fatwa islamqa #6544. A detailed analysis of all known sources of the first hadith can be found on alukah.