The Holy Prophet (s.a.w) understood the nature of reality at its core, therefore, he was able to say what was the truth (al-haqq) or real with certainty:

، كَانَ النَّبِيُّ صلى الله عليه وسلم إِذَا قَامَ مِنَ اللَّيْلِ يَتَهَجَّدُ قَالَ ‏ “‏ اللَّهُمَّ لَكَ الْحَمْدُ، أَنْتَ نُورُ السَّمَوَاتِ وَالأَرْضِ وَمَنْ فِيهِنَّ، وَلَكَ الْحَمْدُ أَنْتَ قَيِّمُ السَّمَوَاتِ وَالأَرْضِ وَمَنْ فِيهِنَّ، وَلَكَ الْحَمْدُ، أَنْتَ الْحَقُّ وَوَعْدُكَ حَقٌّ، وَقَوْلُكَ حَقٌّ، وَلِقَاؤُكَ حَقٌّ، وَالْجَنَّةُ حَقٌّ، وَالنَّارُ حَقٌّ، وَالسَّاعَةُ حَقٌّ، وَالنَّبِيُّونَ حَقٌّ، وَمُحَمَّدٌ حَقٌّ، اللَّهُمَّ لَكَ أَسْلَمْتُ وَعَلَيْكَ تَوَكَّلْتُ وَبِكَ آمَنْتُ، وَإِلَيْكَ أَنَبْتُ، وَبِكَ خَاصَمْتُ، وَإِلَيْكَ حَاكَمْتُ، فَاغْفِرْ لِي مَا قَدَّمْتُ وَمَا أَخَّرْتُ، وَمَا أَسْرَرْتُ، وَمَا أَعْلَنْتُ، أَنْتَ الْمُقَدِّمُ وَأَنْتَ الْمُؤَخِّرُ لاَ إِلَهَ إِلاَّ أَنْتَ ـ أَوْ ـ لاَ إِلَهَ غَيْرُكَ ‏”‏‏.‏

Narrated Ibn `Abbas:

When the Prophet got up at night to offer the Tahajjud prayer, he used to say: O Allah! All the praises are for you, You are the Holder of the Heavens and the Earth, And whatever is in them. All the praises are for You; You have the possession of the Heavens and the Earth And whatever is in them. All the praises are for You; You are the Light of the Heavens and the Earth And all the praises are for You; You are the King of the Heavens and the Earth; And all the praises are for You; You are the Truth and Your Promise is the truth, And to meet You is true, Your Word is the truth And Paradise is true And Hell is true And all the Prophets are true; And Muhammad is true, And the Day of Resurrection is true. O Allah ! I surrender (my will) to You; I believe in You and depend on You. And repent to You, And with Your help I argue (with my opponents, the non-believers) And I take You as a judge (to judge between us). Please forgive me my previous And future sins; And whatever I concealed or revealed And You are the One who make (some people) forward And (some) backward. There is none to be worshipped but you . Sufyan said that `Abdul Karim Abu Umaiya added to the above, ‘Wala haula Wala quwata illa billah’ (There is neither might nor power except with Allah).

Sahih al-Bukhari