Ali ibn Abi Talib, may Allah be pleased with him, would deliver a sermon when the month of Ramadan arrived, saying:
This is the blessed month in which Allah has obligated fasting and not obligated night prayers. Certainly, fasting is not merely from food and drink, but rather from lying, falsehood, and vain talk.
هَذَا الشَّهْرُ الْمُبَارَكُ الَّذِي فَرَضَ اللهُ صِيَامَهُ وَلَمْ يَفْرِضْ قِيَامَهُ أَلَا إِنَّ الصِّيَامَ لَيْسَ مِنَ الطَّعَامِ وَالشَّرَابِ وَلَكِنْ مِنَ الْكَذِبِ وَالْبَاطِلِ وَاللَّغْوِ

Source: al-Sunan al-Kubrá lil-Bayhaqī 7955