The one you already know
Seven verses, said at least seventeen times a day, and the only sūrah a prayer is invalid without.
بِسْمِ ٱللَّهِ ٱلرَّحْمَـٰنِ ٱلرَّحِيمِ ٱلْحَمْدُ لِلَّهِ رَبِّ ٱلْعَـٰلَمِينَ ٱلرَّحْمَـٰنِ ٱلرَّحِيمِ مَـٰلِكِ يَوْمِ ٱلدِّينِ إِيَّاكَ نَعْبُدُ وَإِيَّاكَ نَسْتَعِينُ ٱهْدِنَا ٱلصِّرَٰطَ ٱلْمُسْتَقِيمَ صِرَٰطَ ٱلَّذِينَ أَنْعَمْتَ عَلَيْهِمْ غَيْرِ ٱلْمَغْضُوبِ عَلَيْهِمْ وَلَا ٱلضَّآلِّينَ
Bismillāhi-r-Raḥmāni-r-Raḥīm. Al-ḥamdu lillāhi rabbi-l-ʿālamīn…
“In the name of Allāh,1 the Entirely Merciful, the Especially Merciful.2 [All] praise is [due] to Allāh, Lord1 of the worlds - The Entirely Merciful, the Especially Merciful, Sovereign of the Day of Recompense.1 It is You we worship and You we ask for help. Guide us to the straight path - The path of those upon whom You have bestowed favor, not of those who have earned [Your] anger or of those who are astray.”
Allah says He divided it between Himself and His servant. You say a line; He answers it. Half of it is praise and the last half is the asking.
Source
The Qur'an · 1:1-7
- Qur'anic text in the Uthmani script via Quran.com; translation: Saheeh International