أُوْلَـيِكَThey are...,the Prophets mentioned here, along with their righteous fathers, offspring and brethren,الَّذِينَ هَدَى اللّهُthose whom Allah had guided.meaning, they alone are the people of guidance,فَبِهُدَاهُمُ اقْتَدِهْSo follow their guidance.Imitate them.This command to the Messenger certainly applies to his Ummah, according to what he legislates and commands them.While mentioning this Ayah, Al-Bukhari recorded that;Mujahid asked Ibn Abbas, "Is there an instance where prostration is warranted in (Surah) Sad?"Ibn Abbas said, "Yes."He then recited, وَوَهَبْنَا لَهُ إِسْحَقَ وَيَعْقُوبَAnd We bestowed upon him Ishaq and Ya`qub... until, فَبِهُدَاهُمُ اقْتَدِهْ (...So follow their guidance).He commented,"He (our Prophet, Muhammad) was among them."In another narration, Mujahid added that Ibn Abbas said,"Your Prophet was among those whose guidance we were commanded to follow."Allah's statement,قُل لاَّ أَسْأَلُكُمْ عَلَيْهِ أَجْرًاSay:"No reward I ask of you for this."means, I do not ask you for any reward for delivering the Qur'an to you, nor anything else,إِنْ هُوَ إِلاَّ ذِكْرَى لِلْعَالَمِينَ"It is only a reminder for the Alamin (mankind and Jinns)."so they are reminded by it and guided from blindness to clarity, from misguidance to guidance, and from disbelief to faith