I heard the Messenger of Allah ﷺ say: It is great treachery that you should tell your brother something and have him believe you when you are lying. (Using translation from Abū Dāʾūd 4971)
قَالَ رَسُولُ اللهِ ﷺ كَبُرَتْ خِيَانَةً تُحَدِّثُ أَخَاكَ حَدِيثًا هُوَ لَكَ مُصَدِّقٌ وَأَنْتَ بِهِ كَاذِبٌ