وَإِنَّ مِنكُمْ لَمَن لَّيُبَطِّيَنَّ

There is certainly among you he who would linger behind.

Mujahid and others said,

"this Ayah was revealed about the hypocrites."

Muqatil bin Hayyan said that, 
لَّيُبَطِّيَنَّ
 (linger behind) means,

stays behind and does not join Jihad.

It is also possible that this person himself lingers behind, while luring others away from joining Jihad. For instance, Abdullah bin Ubayy bin Salul, may Allah curse him, used to linger behind and lure other people to do the same and refrain from joining Jihad, as Ibn Jurayj and Ibn Jarir stated. This is why Allah said about the hypocrite, that when he lingers behind from Jihad, then:
 
فَإِنْ أَصَابَتْكُم مُّصِيبَةٌ

If a misfortune befalls you,

death, martyrdom, or - by Allah's wisdom - being defeated by the enemy.
 
قَالَ قَدْ أَنْعَمَ اللّهُ عَلَيَّ إِذْ لَمْ أَكُن مَّعَهُمْ شَهِيدًا
 
 

he says, "Indeed Allah has favored me that I was not present among them."

meaning, since I did not join them in battle. Because he considers this one of Allah's favors on him, unaware of the reward that he might have gained from enduring war or martyrdom, if he was killed