Narrated AbuHurayrah: I heard the Messenger of Allah (ﷺ) say: He then mentioned a tradition like it. This version adds: When they propound that, say: "Say Allah is one. Allah is He to Whom men repair. He has not begotten and He has not been begotten, and no one is equal to Him." Then one should spit three times on his left side and seek refuge in Allah from Satan.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا مُحَمَّدُ بْنُ عَمْرٍو، حَدَّثَنَا سَلَمَةُ، - يَعْنِي ابْنَ الْفَضْلِ - قَالَ حَدَّثَنِي مُحَمَّدٌ، - يَعْنِي ابْنَ إِسْحَاقَ - قَالَ حَدَّثَنِي عُتْبَةُ بْنُ مُسْلِمٍ، مَوْلَى بَنِي تَيْمٍ عَنْ أَبِي سَلَمَةَ بْنِ عَبْدِ الرَّحْمَنِ، عَنْ أَبِي هُرَيْرَةَ، قَالَ سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ فَذَكَرَ نَحْوَهُ قَالَ " فَإِذَا قَالُوا ذَلِكَ فَقُولُوا { اللَّهُ أَحَدٌ * اللَّهُ الصَّمَدُ * لَمْ يَلِدْ وَلَمْ يُولَدْ * وَلَمْ يَكُنْ لَهُ كُفُوًا أَحَدٌ } ثُمَّ لْيَتْفُلْ عَنْ يَسَارِهِ ثَلاَثًا وَلْيَسْتَعِذْ مِنَ الشَّيْطَانِ " .
sunnah.com