وَعَن أم فَرْوَة
قَالَتْ: سُئِلَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: أَيُّ الْأَعْمَالِ أَفْضَلُ؟ قَالَ: «الصَّلَاةُ لِأَوَّلِ وَقْتِهَا»
When asked what act was most excellent, the Prophet (sallallahu alayhi wa sallam) 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 ibn Umar al-Umari who is not considered by traditionists to be strong.
Mishkat al-Masabih 564, Book 5, Prayer, Hadith 42. 1 min read