Mishkat al-Masabih 4 Prayer كتاب الصلاة 42

وَعَن أم فَرْوَة قَالَتْ: سُئِلَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: أَيُّ الْأَعْمَالِ أَفْضَلُ؟ قَالَ: «الصَّلَاةُ لِأَوَّلِ وَقْتِهَا» . رَوَاهُ أَحْمَدُ وَالتِّرْمِذِيُّ وَأَبُو دَاوُدَ وَقَالَ التِّرْمِذِيُّ: لَا يُرْوَى الْحَدِيثُ إِلَّا مِنْ حَدِيثِ عَبْدِ اللَّهِ بْنِ عُمَرَ الْعُمَرِيِّ وَهُوَ لَيْسَ بِالْقَوِيِّ عِنْد أهل الحَدِيث

Umm Farwa said that when asked what act was most excellent, the Prophet replied that it was prayer at the beginning of the proper period for it. Ahmad, Tirmidhi and Abu Dawud transmitted it, and Tirmidhi said that the tradition is transmitted only from the traditions of ‘Abdallah b. ‘Umar al-‘Umari who is not considered by traditionists to be strong.