Reference : Hisn al-Muslim 262

جَاءَ أَعْرَابِيٌّ إِلَى رَسُولِ اللَّهِ صلى الله عليه وسلم فَقَالَ: عَلِّمْنِي كَلاماً أَقُولُهُ: قَالَ: قُلْ (لاَ إِلَهَ إِلاَّ اللَّهُ وَحْدَهُ لاَ شَرِيكَ لَهُ، اللَّهُ أَكْبَرُ كَبِيراً، وَالْحَمْدُ لِلَّهِ كَثِيراً، سُبْحَانَ اللَّهِ رَبِّ العَالَمِينَ، لاَ حَوْلَ وَلاَ قُوَّةَ إِلاَّ بِاللَّهِ الْعَزِيزِ الْحَكِيمِ). قَالَ: فَهَؤُلاَءِ لِرَبِّي، فَمَا لِي؟ قَالَ: قُلْ (اللَّهُمَّ اغْفِرْ لِي، وَارْحَمْنِي، وَاهْدِنِي، وَارْزُقْنِي).
A desert Arab came to Allah's Messenger (ﷺ) and said, "Teach me a word 
that I can say. " The Prophet told him to say:
Lā ilāha illallāh
waḥdahu lā sharīka lah, 
Allāhu Akbaru kabīra, 
walḥamdu lillāhi kathīra, 
Subḥānallāhi Rabbil-`ālamīn, 
Lā ḥawla wa lā quwwata illā billāhi ‘l-`Azīzil-Hakīm.

He said, "That is for my Lord, but what about me?" The Prophet (ﷺ) told 
him to say:
Allāhummaghfir lī, warḥamnī, waḥdinī warzuqnī.

A desert Arab came to Allah's Messenger (ﷺ) and said, "Teach me a word that I can say. " The Prophet told him to say:

There is none worthy of worship but Allah, Who has no partner, 
Allah is the Great, the Most Great, 
and praise is to Allah in abundance, 
glory is to Allah, Lord of the worlds. 
There is no power and no might but by Allah the Mighty, the Wise.

He said, "That is for my Lord, but what about me?" The Prophet (ﷺ) told him to say:

O Allah forgive me, and have mercy on me and guide me, and provide for me.

Reference:
Muslim 4/2072, Abu Dawud reports the same Hadith with the addition: and 
when the Arab left, the Prophet (ﷺ) said: "He has filled his hands with 
goodness." 1/220.

Chapter: Excellence of Tasbih, Tahmid, Tahlil, and Takbir