I have a co-wife. Is there any harm for me if I give her the false impression (of getting something from my husband which he has not in fact given me)? Thereupon Messenger of Allah ﷺ said: The one who creates such a (false impression) of receiving what one has not been given is like one who wears the garment of falsehood. (Using translation from Muslim 2130a)
أَنَّ امْرَأَةً جَاءَتْ إِلَى رَسُولِ اللهِ ﷺ فَقَالَتْ يَا رَسُولَ اللهِ إِنَّ لِي جَارَةً فَهَلْ عَلَيَّ مِنْ جُنَاحٍ أَنْ أَتَشَبَّعَ مِنْ زَوْجِي بِمَا لَمْ يُعْطِنِي؟ فَقَالَتْ قَالَ رَسُولُ اللهِ ﷺ إِنَّ الْمُتَشَبِّعَ بِمَا لَمْ يُعْطَ كَلَابِسِ ثَوْبَيْ زُورٍ