one who does not give thanks to people does not give thanks to Allah
(Subhanahu wa Tala)" - Reported by Bukhari in al-Adab al-Mufrad.
The Prophet, salah allahu 'alayhi wa salam, said:
“Whoever has a favour done for him and says Jazaak Allaahu khayran (may
Allaah reward you with good) has done his utmost to thank him.”Narrated
by al-Tirmidhi, 2035; classed as saheeh by al-Albaani in Saheeh