Agreed upon.

Explanation
The author, al-Nawawī (may Allah have mercy on him), places in his Riyāḍ al-Ṣāliḥīn a chapter entitled “The Excellence of the Fajr and ʿIshāʾ Prayers,” meaning when they are performed in congregation. He singled out these two prayers because of the abundance of reward they carry. In the ḥadīth of ʿUthmān ibn ʿAffān (may Allah be pleased with him) it is stated that when a person performs the ʿIshāʾ and Fajr prayers in congregation, it is as though he has spent the entire night in worship: ʿIshāʾ accounts for half the night and Fajr for the other half. This is a tremendous virtue—it is as if you have stood in prayer the whole night while reclining in your bed, provided you pray Fajr and ʿIshāʾ in congregation.

The Prophet ﷺ also said, in the ḥadīth of Abū Hurayrah, “If people knew the blessing contained in al-ʿAtamah (the ʿIshāʾ prayer) and the Fajr prayer, they would come to them even if they had to crawl.” Al-ʿAtamah refers to ʿIshāʾ, and Fajr is well known. Were they to realise the reward and recompense stored in them, they would crawl across the ground to attend—just as a child crawls—because of the immense reward they hold.

Likewise, another ḥadīth related by Abū Hurayrah states that the prayers most burdensome to the hypocrites are the ʿIshāʾ and Fajr prayers. This is because hypocrites only pray to be seen and heard; ʿIshāʾ and Fajr are offered in darkness where they cannot be observed, so they attend them reluctantly. In contrast, they readily come to Ẓuhr, ʿAṣr, and Maghrib because people can see them, for they merely seek to impress others and remember Allah but little. For ʿIshāʾ and Fajr, there is no room for ostentation, as they are performed in darkness, and in the Prophet’s ﷺ time there were no lamps or lights, so no one could see them—hence their attendance at ʿIshāʾ