Quran 7:21 from Surah Al-A'raaf on Divine Marvels.
وَقَاسَمَهُمَآ إِنِّي لَكُمَا لَمِنَ ٱلنَّٰصِحِينَ
English translation: And he swore (to) both of them Indeed I am to both of you among the sincere advisers
Transliteration: waqasamahuma inni lakuma lamina al-nasihina