Fulfilling rights of the ungrateful as idolatry
Nahj al-Balāgha|Volume 1|Book 3|Chapter 164
١٦٤. وَقَالَ (عليه السلام): مَنْ قَضَى حَقَّ مَنْ لَا يَقْضِي حَقَّهُ فَقَدْ عَبَدَهُ.
164. Amīr al-mu’minīn, peace be upon him, said: He who fulfils the right of a man who does not fulfil his right, (is as though he) worships him.