Mishkat al-Masabih

‘Abdallah b. ‘Amr reported God's messenger as saying that “Praise be to God” is the beginning of thanksgiving, for the man who does not praise God has not thanked Him.

وَعَنْ عَبْدِ اللَّهِ بْنِ عَمْرٍو قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «الْحَمْدُ رَأْسُ الشُّكْرِ مَا شَكَرَ اللَّهَ عَبْدٌ لَا يحمده»