KAWTHAR OR KAWSAR
Surah al-Kawthar is the 108th Surah of the Qur'an, and the shortest surah of the Qur’an. This Surah was revealed in Makkah.
The meaning of the word ‘Kawthar’ means Abundance.
It is a river in Paradise which Allah سبحانه و تعالىhas given to His Prophet Muhammad ﷺ. This meaning is what is meant in the ayath where Allah سبحانه و تعالىsays (interpretation of the meaning):
Translation of the Surah
108:2 - So pray to your Lord and sacrifice [to Him alone].
108:3 - Indeed, your enemy is the one cut off.
This is how the Prophet Muhammad ﷺinterpreted it. It was narrated by Sahih Al-Muslim in his Saheeh H:607 that Anas رضي الله عنهsaid: Whilst we were with the Prophet Muhammad ﷺ, he dozed off then he raised his head and he was smiling. We said, “Why are you smiling, O Messenger of Allah سبحانه و تعالى?” He said: “A soorah has been revealed to me.” And he recited (interpretation of the meaning): “Verily, We have granted you (O Muhammad ﷺ) Al-Kawthar (a river in Paradise)…” [Qur’an.Surah Kawthar 108:1]
to the end of the soorah. Then he said: “Do you know what is al-Kawthar?” We said: Allah سبحانه و تعالى and His Messenger Muhammad ﷺknow best.” He said: “It is a river that my Lord has promised to me in which there is much goodness. And it is a cistern to which my ummah will come on the Day of Resurrection.”
Al-Tirmidhi رحمت اللهnarrated from Ibn ‘Umarرضي الله عنهthat the Prophet Muhammad ﷺsaid: “Al-Kawthar is a river in Paradise. Its banks are made of gold and its bed is of pearls and rubies…” Al-Tirmidhi رحمت اللهsaid: It is hasan saheeh; it was classed as Saheeh by al-Albaani رحمت اللهin Saheeh Sunan Al-Tirmidhi 3:135 (NE 3284)
Narrated Anas bin Malikرضي الله عنه: The Prophet Muhammad ﷺsaid: "While I was walking in Paradise (on the night of Mi'raj), I saw a river, on the two banks of which there were tents made of hollow pearls. I asked, "What is this, O Gabriel عليه السلام?' He said, 'That is the Kauthar which Your Lord has given to you.' Behold! Its scent or its mud was sharp smelling musk!" (The sub-narrator, Hudba is in doubt as to the correct expression. Sahih al-Bukhari 6581 (Vol. 8:583)
Abu Hazim رضي الله عنهadded: An-Nu`man bin Abi `Aiyash رضي الله عنه, on hearing me, said. "Did you hear this from Sahl رضي الله عنه?" I said, "Yes." He said, " I bear witness that I heard Abu Sa`id Al-Khudriرضي الله عنهsaying the same, adding that the Prophet Muhammad ﷺsaid: 'I will say: They are of me (i.e. my followers). It will be said, 'You do not know what they innovated (new things) in the religion after you left'. I will say, 'Far removed, far removed (from mercy), those who changed (their religion) after me." Sahih al-Bukhari 6584 (Vol. 8: 586) 
English Translation of the Qur’an from Sahih International