An-Nisa: 150
"Indeed, those who disbelieve..."
He has categorized those who believe in Allah but disbelieve in His messengers, or those who believe in Allah and some of His messengers while disbelieving in others, as being disbelievers in Allah and all His messengers combined, for the reason we have previously mentioned.
The meaning of "wishing to take a way between that" is that they intend to adopt a religion that is intermediate between belief and disbelief. This is like His saying:
"And do not recite [too] loudly in your prayer, nor recite quietly, but seek a way between that." (Al-Isra: 110)
Meaning: a middle path in recitation, which is between loud recitation and whispering.
They have erred, for there is no middle ground between disbelief and belief. Therefore, He said:
**"Those are the disbelievers, truly."**
Meaning: they are the ones who are complete in their disbelief.
"Truly" (haqqan) is an emphasis on the content of the sentence, just as you would say, "He is the servant of Allah, truly," meaning that this fact is true. It refers to their state of being complete in disbelief. Alternatively, it is an adjective for the verbal noun implied by "disbelievers," meaning: they are those who have disbelieved a true, established, and certain disbelief, in which there is no doubt.