What is the ruling regarding catching a part of Asr or Fajr prayer before their respective prescribed times end?
Chapter on Prayer Times
Al-Mughni
Book of Prayer
Primary text
Whoever catches one prostration (sujud) of the Asr prayer before sunset must complete his prayer. Similarly, whoever catches one prostration of the Fajr prayer before sunrise must complete his prayer. This is supported by the narration of Abu Hurairah, which is agreed upon (Muttafaqun 'alayh), and in Al-Nasa'i's narration, the text states: 'he has caught it' (faqad adrakaha). Because when attaining a ruling concerning the prayer is connected to an act, the rak'ah and less than it are equal, such as catching the congregation or a traveler catching the resident's prayer.
Supporting text
The restrictive meaning (mafhum) of the first narration regarding the rak'ah is superseded by the explicit statement (mantuq), and explicit statements take precedence over restrictive meanings. Analogy (Qiyas) is invalidated because catching one rak'ah without catching the Tashahhud of that rak'ah is permissible under the majority view, which contradicts the analogy.