Whoever prays the two cool prayers
مَنْ صَلَّى الْبَرْدَيْنِ دَخَلَ الْجَنَّةَ
Man salla-l-bardayni dakhala-l-jannah.
"Whoever prays the two cool prayers will enter Paradise."
Narrated by Abu Musa al-Ash'ari. Sahih al-Bukhari 574, Sahih Muslim 635
A short reflection
Fajr and Asr. The two hardest. One is too early, the other interrupts the working day. The reward is named in full.