Among you is he who lags behind. Then, when a calamity befalls you, he says, God has favored me, that I was not martyred with them.

So those who sell the life of this world for the Hereafter, must fight in Allah's cause and We shall bestow a great reward upon whoever fights in Allah's cause, whether he is martyred or is victorious.

Rejoicing in what Allah has bestowed upon them of His bounty, and they receive good tidings about those to be martyred after them who have not yet joined them that there will be no fear concerning them, nor will they grieve.

They rejoice in what Allah has bestowed upon them of His Bounty, rejoicing for the sake of those who have not yet joined them, but are left behind (not yet martyred) that on them no fear shall come, nor shall they grieve.

And Mohammed (peace and blessings be upon him) is purely a Noble Messenger there have been Noble Messengers before him so if he departs or is martyred, will you turn back on your heels? So whoever turns back on his heels does not cause any harm to Allah and Allah will soon reward the thankful. ( Neither God nor an angel, but a human being with the highest spiritual status.)

Among the believers are men who have been true to their covenant with Allah i.e. they have gone out for Jihad (holy fighting), and showed not their backs to the disbelievers , of them some have fulfilled their obligations (i.e. have been martyred), and some of them are still waiting, but they have never changed i.e. they never proved treacherous to their covenant which they concluded with Allah in the least.