إِذَا أَدْرَكَ الرَّجُلُ بَعْضَ الصَّلَاةِ وَ فَاتَهُ بَعْضٌ[2] خَلْفَ إِمَامٍ يَحْتَسِبُ بِالصَّلَاةِ خَلْفَهُ[3] جَعَلَ مَا أَدْرَكَ أَوَّلَ صَلَاتِهِ إِنْ أَدْرَكَ مِنَ الظُّهْرِ أَوِ الْعَصْرِ أَوِ الْعِشَاءِ الْآخِرَةِ رَكْعَتَيْنِ وَ فَاتَتْهُ رَكْعَتَانِ قَرَأَ فِي كُلِّ رَكْعَةٍ مِمَّا أَدْرَكَ خَلْفَ الْإِمَامِ فِي نَفْسِهِ بِأُمِّ الْكِتَابِ[4]- فَإِذَا سَلَّمَ الْإِمَامُ قَامَ فَصَلَّى الْأَخِيرَتَيْنِ
Umar ibn Udhayna narrated from Zurarah by Imam Muhammad ibn Ali Al-Baqir (a.s) that He said: "If a person joins a congregational prayer after some of it has passed but counts their prayer as valid behind the Imam, then what they have caught counts as the beginning of their prayer. For example, if they join the Dhuhr, A