فَمَهِّلِ الْكَافِرِينَ
...
So, give a respite to the disbelievers;
meaning, wait for them and do not be in haste concerning them.
...
أَمْهِلْهُمْ رُوَيْدًا
deal gently with them for a while.
meaning, a little while.
This means that you will see what befalls them of torment, punishment and destruction.
This is as Allah says,
نُمَتِّعُهُمْ قَلِيلً ثُمَّ نَضْطَرُّهُمْ إِلَى عَذَابٍ غَلِيظٍ
We let them enjoy for a little while, then in the end We shall oblige them to (enter) a great torment. (31:24)
This is the end of the Tafsir Surah At-Tariq, and unto Allah is all praise and thanks.