Silsilah as-Sahihah 2846 — Etiquettes of the Mosque

Muawiyah bin Qurrah narrates from his father that the Messenger of Allah (peace and blessings be upon him) said: "Whoever eats the fruit of these two disliked (and harmful, i.e., onion and garlic) trees, should by no means come near our mosque. If you must eat these things, then cook them to remove their odor."