Mu'awiyah ibn Haydah

Muʿāwiyah ibn Ḥaydah came to Madinah among the delegations from Yemen and, so far as we know, saw the Prophet ﷺ only that once. He asked what must be covered of the ʿawrah and from whom, and was told to guard it from everyone but one's spouse. He then asked what a man should do when he is entirely alone, and the answer is the one the fiqh books turn on: اللَّهُ أَحَقُّ أَنْ يُسْتَحْيَا مِنْهُ, Allah has more right that you feel shy before Him.

His narration is the single explicit ḥadīth on the ʿawrah, and it comes from one of these one-time Companions of the delegations, which is the shaykh's point about them: they came to study fiqh and ʿaqīdah, and what they carried home became the standard evidence.