The hadeeth about saying “Allaahumma ajirni min al-naar” seven times

This hadeeth was narrated by Imam Ahmad in al-Musnad, 17362, and by Abu Dawood, 5079. The hadeeth is as follows:

It was narrated that the Prophet (peace and blessings of Allaah be upon him) said: “When you pray Fajr, then say before speaking to any of the people, ‘Allaahumma ajirni min al-naar (O Allaah, protect me from the Fire)’ seven times. Then if you die on that day, Allaah will grant you protection from the Fire. And when you pray Maghrib, then say before speaking to any of the people, ‘Allaahumma inni as’aluka al-jannah, Allaahumma ajirni min al-naar (O Allaah, I ask You for Paradise, O Allaah, protect me from the Fire)’ seven times. Then if you die that night, Allaah will grant you protection from the Fire.”
Two things may be noted about the hadeeth.
1.     It does not say that this du’aa’ is to be said after ‘Isha’, as mentioned in the question.
2.     The hadeeth is not saheeh in its narration from the Prophet (peace and blessings of Allaah be upon him). See al-Silsilah al-Da’eefah by Shaykh al-Albaani (may Allaah have mercy on him), 1624.
Based on this, it is not mustahabb to recite this du’aa’ after Fajr and Maghrib prayers.
3.     It was narrated that Anas (may Allaah be pleased with him) said: The Prophet (peace and blessings of Allaah be upon him) said: “Whoever asks Allaah for Paradise three times, Paradise will say, ‘O Allaah, admit him to Paradise.’ Whoever seeks protection from the Fire three times, Hell will say, ‘O Allaah, protect him from the Fire.’”
Narrated by al-Tirmidhi, 2572; Ibn Maajah, 4340. This is a saheeh hadeeth; it was classed as saheeh by Shaykh al-Albaani (may Allaah have mercy on him) in Saheeh al-Jaami’, 6275).
But there is nothing to state that this should be recited in conjunction with any particular prayer, or at any particular time.
It is mustahabb for the believer to ask Allaah for Paradise a great deal, and to seek protection from Hell a great deal, without saying such words in conjunction with any particular prayer, or at any particular time.
 And Allaah knows best.

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