Verse [ 100:5] فَوَسَطْنَ بِهِ جَمْعًا (then enter, at the same time, into the centre of the [ opposing ] host) In other words, they penetrate into the centre of the enemy forces without the least degree of fear.
The word kanud, (100:6) according to Hasan Basri (رح) ، refers to the one who counts the calamities that befall him, and forgets Allah's favours. Abu Bakr Wasiti said that kanud is the one who spends the bounties of Allah for sinful purposes. Tirmidhi said that kanud is the one who looks at the bounty, and not at the Bounteous Lord. In short, all these interpretations lead to the sense of 'ungratefulness to favours and bounties' and hence the expression kanud means 'ungrateful'.