In his Tafsir, As-Suddi reported that Ibn `Abbas and Ibn Mas`ud commented on;

أُوْلَـئِكَ الَّذِينَ اشْتَرَوُاْ الضَّلَـلَةَ بِالْهُدَى

(These are they who have purchased error with guidance) saying it means, "They pursued misguidance and abandoned guidance. " Mujahid said, "They believed and then disbelieved," while Qatadah said, "They preferred deviation to guidance." Qatadah's statement is similar in meaning to Allah's statement about Thamud,

The ninth verse shows the basic denseness of the hypocrites - how they failed to make use of the ordinary sense of discrimination. They had grown up in a pagan society, and knew very well what the way of the infidels was. Now they had become familiar enough with Islam too, and could easily see the difference. But, in their greed, and for the sake of petty worldly profit, they still chose disbelief as against Islam, and bartered away something as invaluable as Iman ایمان (faith) for something as worthless, and even harmful as kufr کفر (infidelity). In giving the name of 'trade' or 'commerce' to this action, the Holy Qur'an suggests that these worldly-wise men had no understanding even of the art of trading.