Surah Al-Layl 92:6
وَصَدَّقَ بِٱلْحُسْنَىٰ
And believes in the best [reward],
Translation: Saheeh International
Tafsir
and affirms the truth of the best word that is the truth of ‘there is no god but God’ in both places here and below verse 9
Excerpt from Tafsir al-Jalalayn, commentary on 92:6, via Quran.com. The reader has the full commentary and 9 more tafsirs.