Allah said,

أُوْلَـئِكَ الَّذِينَ اشْتَرُوُاْ الضَّلاَلَةَ بِالْهُدَى ...

These are they who have purchased error with guidance,

In his Tafsir, As-Suddi reported that Ibn Abbas and Ibn Mas`ud commented saying it means,

"They pursued misguidance and abandoned guidance.''

Mujahid said,

"They believed and then disbelieved,''

while Qatadah said,

"They preferred deviation to guidance.''

This statement is similar in meaning to Allah's statement about Thamud,

وَأَمَّا ثَمُودُ فَهَدَيْنَـهُمْ فَاسْتَحَبُّواْ الْعَمَى عَلَى الْهُدَى

And as for Thamud, We granted them guidance, but they preferred blindness to guidance. (41:17)

In summary, the statements that we have mentioned from the scholars of Tafsir indicate that the hypocrites deviate from the true guidance and prefer misguidance, substituting wickedness in place of righteousness. This meaning explains Allah's statement, أُوْلَـئِكَ الَّذِينَ اشْتَرُوُاْ الضَّلاَلَةَ بِالْهُدَى (These are they who have purchased error with guidance),

meaning, they exchanged guidance to buy misguidance. This meaning includes those who first believed, then later disbelieved, whom Allah described,

ذَلِكَ بِأَنَّهُمْ ءَامَنُواّ ثُمَّ كَفَرُوا فَطُبِعَ عَلَى قُلُوبِهِمْ

That is because they believed, and then disbelieved; therefore their hearts are sealed. (63:3)

The Ayah also includes those who preferred deviation over guidance. The hypocrites fall into several categories.

This is why Allah said,

... فَمَا رَبِحَت تِّجَارَتُهُمْ وَمَا كَانُواْ مُهْتَدِينَ ﴿١٦﴾

So their commerce was profitless. And they were not guided,

meaning their trade did not succeed nor were they righteous or rightly guided throughout all this.

In addition, Ibn Jarir narrated that Qatadah commented on the Ayah,

"By Allah! I have seen them leaving guidance for deviation, leaving the Jama`ah (the community of the believers) for the sects, leaving safety for fear, and the Sunnah for innovation.''

Ibn Abi Hatim also reported other similar statements.