Prophet Muhammad (SAW) said: “Whoever eats onions, garlics or leeks should not approach out mosque for the angels are offended by whatever offends the children of Adam.” Sahih Muslim.
So when we are about to pray, whether it is in the home or in the mosque, we should freshen our breath. Prophet Muhammad (SAW) used to freshen his breath before each prayer to prepare himself for the conversation with Allah.
When we stand in prayer, the angel stands behind us listening to the the recitation. Then the angel draws near until the angel’s mouth is on the mouth of the reciter. So when the reciter is reciting Quran it goes straight to the heart of the angel. So we should keep our mouths fresh and clean when we recite the Quran.