When their most wicked went forth.
meaning, the most wicked person of the tribe, and he was Qudar bin Salif, the one who killed the she-camel. He was leader of the tribe of Thamud, and he is the one whom Allah refers to in His saying,
فَنَادَوْاْ صَـحِبَهُمْ فَتَعَاطَى فَعَقَرَ
But they called their comrade and he took (a sword) and killed (her). (54;29)
This man was mighty and respected among his people. He was of noble lineage and a leader who was obeyed.
This is just as Imam Ahmad recorded from `Abdullah bin Zam`ah. He said that the Messenger of Allah gave a sermon in which he mentioned the she-camel and he mentioned the man who killed her. Then he said,
إِذِ انبَعَثَ أَشْقَـهَا
(When their most wicked went forth.)
انْبَعَثَ لَهَا رَجُلٌ عَارِمٌ عَزِيزٌ مَنِيعٌ فَي رَهْطِهِ مِثْلُ أَبِي زَمْعَة
A strong and mighty man who was invincible among his tribe, like Abu Zam`ah, went forth to her.
This Hadith was recorded by Al-Bukhari in his Book of Tafsir, and Muslim in his Book of the Description of the Hellfire.
At-Tirmidhi and An-Nasa'i both recorded it in their Sunans in their Books of Tafsir.
The Story of Salih's She-Camel
Allah then says