وَعَنْ أَبِي هُرَيْرَةَ رَضِيَ اللَّهُ عَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: مَنْ أَدْرَكَ رَكْعَةً مِنَ الصَّلَاةِ مَعَ الإِمَام فقد أدْرك الصَّلَاة كلهَا "
Abu Huraira reported God’s Messenger as saying, “If anyone is in time for a rak‘a in the prayer along with the imam he has said the whole prayer.” (Bukhari and Muslim.)