أَفْضَلُ الذِّكْرِ لَا إِلَهَ إِلَّا اللَّهُ، وَأَفْضَلُ الدُّعَاءِ الْحَمْدُ لِلَّهِ (Tirmidhi)
Translation: The best remembrance is “There is no deity worthy of worship except Allah,” and the best supplication is “All praise belongs to Allah.”
أَفْضَلُ — best or most excellent; الذِّكْرِ — of remembrance; الدُّعَاءِ — of supplication; الْحَمْدُ لِلَّهِ — all praise is for Allah.
Brief grammar: أَفْضَلُ الذِّكْرِ is an iḍāfah: أَفْضَلُ is an elative form and الذِّكْرِ the genitive complement. The same construction appears in أَفْضَلُ الدُّعَاءِ.
لَا إِلَهَ إِلَّا اللَّهُ affirms Allah's oneness, while الْحَمْدُ لِلَّهِ expresses praise and gratitude to Him.