«فَلَا يَخْدَعَنَّكَ لُمُوعُ السَّرَابِ»
Do not let the shimmer of a mirage deceive you.
Sarāb is a mirage; lumūʿ a gleam or glitter. Office may look rewarding at a distance while concealing restrictions or disappointments.
Lā yakhdaʿannaka is an emphatic prohibition. The image gathers the argument of the poem into one lesson about appearances: the brightness of an opportunity does not guarantee its substance or durability.