[2:16] Those are they who have bought error for guidance; so their commerce has not profited them; nor are they guided.
The allusion in it is that those who have neglected what is due (ḥuqūq) by remaining in the familiar territories of worldly fortunes (ḥuẓūẓ) have lost their bargain, so their commerce has not profited them. Those who are content with this world over the next are in manifest loss. Those who prefer this world or the next over the Real have the most intense loss. Although the one who suffers the loss of [the Gardens] of bliss will come up short, the one who is afflicted with distance from intimate conversation and with disengagement in his heart from his Protector, who remains in the captivity of carnal desires with no messenger to his heart, no attainment for his spirit, no intimate conversation with Him, no approach to Him, no witnessing in his innermost self - this is the one who [truly] suffers and is afflicted. If even a moment slips away, his Lord has slipped away. Moments have no substitutes or alternates. Thus someone said:
You were the pupil
of my eye.
[The organ] by which I see
wept for you.
Anyone who has a will after you,
let him die,
for I used to be
a guard over you.