فَمَهِّلِ الْكَافِرِينَ أَمْهِلْهُمْ رُوَيْدًا
So grant the disbelievers respite; give them a little respite. (At-Tariq 86:17)
Famahhil and amhilhum both command the granting of respite. The second does not introduce a separate subject: it reinforces the instruction and ruwaydan specifies the short interval.
Morphology: Mahhil is an imperative of Form II, while amhil is from Form IV. Their related meaning, repeated through distinct forms, lends force and attention to the instruction.