Benefits courtesy of Shaykh Zayd ibn Hādi Al-Madkhalī derived from the hadīth:

The Messenger of Allāh – sallallāhu alaihi wa sallam – said:

“He does not thank Allāh, he who does not thank the People.” (1)

From the Islamic mannerisms which are befitting for a Muslim to adhere to, is to show gratefulness to the one who was good towards you,  any type of goodness, whether it was by (sharing) knowledge or commanding good and forbidding evil; or by doing good in fulfilling a person’s needs.

جزاك الله خيرا

Allāh reward you with good

If you said that to him, indeed you have excelled/done your utmost in praising him and thanking him.

As for the one who does good to you and you didn’t thank him, or mention him with good, then this is a blessing a person has been ungrateful towards . Oh Muslim, it is not from Islamic manners to reject some goodness which someone – whether close to you or far from you –  has done to you.

And this is the meaning of the hadīth:

“Whoever does not thank the people has not thanked Allāh.”

Allāh is The Bestower of Blessings; The Most Great; The Good Doer (to His Slaves); The Generous; the people likewise are good doers within the limits of their ability. i.e. some of them are good to others. So whoever has good done to him by people then it is from Islamic etiquettes to thank them for being good towards him – whatever type of goodness it may be, the Messenger of Allāh said “Indeed Allāh has prescribed goodness/perfection (ihsān) on everything”. (2)

And from the errors made is that the one who is close to you (friend/relative etc) or far from you; does good to you and you do not thank him for his goodness nor mention him with good in order that supplication can be made for him.

‘Awn Al-Ahad As-Samad Sharh Al-Adab Al-Mufrad of Shaykh Zayd ibn Hādi Al-Madkhalī Page 242

(1) Abū Dāwud- hadith no.4811, At-Tirmidhī- hadith no. 1954, Ahmad- hadith no.7939.  Saheeh – Authenticated by Al-Albāni
(2) Saheeh Muslim Hadith no. 1955