Must a traveler complete the prayer when praying behind a resident (muqim)?
Chapter on the Traveler's Prayer
Al-Mughni
Book of Prayer
Primary text
A traveler joining a resident (muqim) in prayer must complete the full prayer (I'timaam). This applies whether the traveler joins for the entire prayer, one rak'ah, or less than that. This ruling is supported by the practice narrated from Ibn Umar and Ibn Abbas, and a group of the Tabi'in, and is held by al-Thawri, al-Awza'i, al-Shafi'i, Abu Thawr, and the People of Opinion. The primary evidence is the narration from Ibn Abbas stating that the difference between the traveler praying two rak'ahs alone and four behind a resident is due to 'that is the Sunnah,' which refers to the Sunnah of the Messenger of Allah (peace be upon him). Furthermore, Ibn Umar prayed four rak'ahs when leading or following a resident, and two when praying alone, as narrated by Muslim. This prayer, being reduced from four to two units when alone, cannot be prayed as two behind someone praying four, unlike the Friday prayer.
Supporting text
Dissenting views exist. Ishaq permits Qasr because the prayer is valid as two rak'ahs when prayed alone, and following a resident should not increase it, similar to the dawn prayer (Fajr). Al-Tawus, al-Sha'bi, and Tamim bin Hudhal permitted two rak'ahs if the traveler joins two rak'ahs of the resident's prayer. Al-Hasan, al-Nakha'i, al-Zuhri, Qatadah, and Malik hold that if the traveler joins one rak'ah, they complete it, but if they join less than one, they shorten it, based on the Hadith: 'Whoever catches a rak'ah of the prayer has caught the prayer,' and the precedent set by the Friday prayer.