Understand with ease.

Surah Al Kawthar (The Abundance)

Bismillaahir Rahmaanir Raheem

Innaa a'taina kal kauthar

Fa salli li rabbika wanhar

Inna shani-aka huwal abtar

Surely (O Muhammad) We have given you abundance (of good (Kawthar).

Therefore to your Lord turn in Prayer and Sacrifice.

Surely your enemy is the one who will be cut off.

The following is a story told about the occasion of the revelation of Surah Kawthar: 'As-ibn-wa'il, who was one of the chiefs of the pagans, met the holy Prophet (SAWW) coming out of the Sacred Mosque. He spoke with him (SAWW) for awhile.

In the meantime, a group of authoritative men of the Quraish were sitting in the Mosque watching him from a distance.

When 'As-ibn-Wa'il entered the Mosque they asked him:

"To whom were you speaking?"

He answered:

"With this abtar one".

He used this word for the holy Prophet (SAWW) to taunt him, because he  had two sons born of  Khadijah: Qasim and  'Abdullah who died in Mecca and so, there was no live male issue from the holy Prophet (SAWW). Hence after, the Qur'an applied this name to the enemies of the Prophet.

The Arabs used to call the one who had no son as abtar. So, then it means the one whose succession in his seed has ceased, i.e., the one who has none to inherit him. To console the holy Prophet (SAWW), this Surah was revealed with the glad tidings of the greatest amount or the highest degree of the grace of Allah, bestowed on him.

Those people traditionally considered the male child extraordinarily valuable and thought of him as a substitute for the father. They happily imagined that with the demise of the Holy Prophet (SAWW) his program would cease because he had no son to substitute him to continue it.

The revelation of this Surah was, in fact, an answer to the enemies of the Apostle to inform them that Islam and the Qur'an would remain and ceaselessly continue, forever whereas the enemy of Islam shall be cut off from this Dunya and in Aakhirah.

Source: Abul A'la Maududi, Tafhim al-Qur'an - The Meaning of the Qur'an