Thanking people is part of thanking Allah

Narrated Abu Hurairah (ra): The Prophet (sa) said, “He has not thanked Allah who has not thanked people.”

[Sunan Abu Dawud, Book of Manners, #4811]

عَنْ أَبِي هُرَيْرَةَ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ‏ لاَ يَشْكُرُ اللَّهَ مَنْ لاَ يَشْكُرُ النَّاسَ