Whenever anyone does something for us and we need to thank them, the best words we can say to them are Jazakallah
Jazakallah means, ‘May Allah reward you’
By saying Jazakallah:
1) We will get reward for remembering Allah Ta’aala (making zikr)
2) We will get the reward of following a sunnah
3) We are telling Allah Ta’aala to reward the person who has been kind to us.
Sayyiduna Usāmah bin Zayd رضي الله عنه reports that Nabi ﷺ said, “Whoever says Jazākallāhu Khayrā to the one who has done good to him has certainly extolled him in praise.” (Sunan Tirmidhi)