Musnad Ahmad 32:672

Husayn ibn Muhammad narrated to us, Khalaf narrated to us, from Hafs, from Anas ibn Malik, that he said: We set out to Ash-Sham to ‘Abd al-Malik, and we were forty men from the Ansar, so that he would assign us our stipends. When he returned and we were at Faj al-Naqah, he prayed the Dhuhr prayer with us as two rak'ahs, then he performed the taslim and entered his tent. The people stood up, adding two more rak'ahs to his two rak'ahs. He said: So he said, "May Allah make the faces ugly! By Allah, they have neither attained the Sunnah nor accepted the concession. I bear witness that I heard the Messenger of Allah (ﷺ) say: 'There will be people who delve too deeply into the religion; they will pass through it just as an arrow passes through the game.'"