Event of Mubahalah

In the south of Arabia, there is a place called Najran. There lived the Christian tribe of Najran who staunchly believed that Prophet Isa (a) i.e. Jesus was the son of God. The Prophet invited them to accept Islam. In response to that, a delegation of their priests and elders came to Madina. They wanted to discuss religion with the Holy Prophet Prophet Muhammad (S).

Their argument was that Jesus was born without a father, so he was the son of God. The Holy Prophet explained to them that just as Allah created Prophet Adam without a father or even a mother, in the same way He created Jesus without a father. Hence Jesus was a servant of Allah as was Prophet Adam. The Christians did not agree with this simple truth. They stuck to their belief that Jesus was the son of God

Their argument was that Jesus was born without a father, so he was the son of God. The Holy Prophet explained to them that just as Allah created Prophet Adam without a father or even a mother, in the same way He created Jesus without a father. Hence Jesus was a servant of Allah as was Prophet Adam. The Christians did not agree with this simple truth. They stuck to their belief that Jesus was the son of God. The Prophet asked them to wait. Then came the following Revelation (message from Allah):

O Messenger! If they dispute with you in this matter after the knowledge has come to you, then, say, 'Come, let us call our sons and your sons, and our women and your women, and our souls and your souls. Then let us earnestly invoke and lay the malison (curse) of Allah on those who lie”. [1]

It was then agreed that the Christians seek MUBAHALA with the Prophet. The meaning of MUBAHALA is that both of them invoke from Allah that he, who speaks the truth may survive and he, who is untrue may perish.
On the day of Mubahala, the Prophet of Islam took with him his grandsons - Imam Hasan (a) and Imam Husain (a), his daughter Fatima Zehra (a) and his cousin and son-in-law Imam Ali (a). But on seeing the radiant faces of these sinless members of the household of the Prophet, the Christians got scared. They decided not to seek Mubahala anymore but accepted their defeat. They agreed to pay tribute and returned home.

On the day of Mubahala, the Prophet of Islam took with him his grandsons - Imam Hasan (a) and Imam Husain (a), his daughter Fatima Zehra (a) and his cousin and son-in-law Imam Ali (a). But on seeing the radiant faces of these sinless members of the household of the Prophet, the Christians got scared. They decided not to seek Mubahala anymore but accepted their defeat. They agreed to pay tribute and returned home.

The Prophet, before going for Mubahala, was commanded by Allah to take with him his sons, his women and his souls. The Holy Prophet obeyed this command as under:
In place of his sons, he took with him Imam Hasan (a) and Imam Husain (a). In place of women, he took Fatima Zahra (a). In place of his souls, he took Imam Ali (a).
This is how he showed to the world who the true and real members of his Ahlul Bait (People of the House of Prophet) were. To love them has been obligatory (wajib) command of Allah on every Muslim. The Holy Quran says:

Say, ‘I do not ask you any reward for it (messengership) except the love of [my] relatives.’[2]

The Prophet and his Ahlul Bait sacrificed all the worldly comforts and even their lives in order to convey the true religion of Islam to us. In return of their sacrifices, we are commanded by God to love them. The aim is that through their love, we follow their footsteps. We follow the true teachings of Islam taught by them, so that we live a good and decent life in this world and earn the pleasure of God in the life hereafter.

The Prophet and his Ahlul Bait sacrificed all the worldly comforts and even their lives in order to convey the true religion of Islam to us. In return of their sacrifices, we are commanded by God to love them. The aim is that through their love, we follow their footsteps. We follow the true teachings of Islam taught by them, so that we live a good and decent life in this world and earn the pleasure of God in the life hereafter.

Why was Imam Ali included?

The Almighty commanded His Messenger to say to the delegation of Najran: "Come! We will summon our Sons and your Sons, our women and your women; and ourselves and yourselves...."

In compliance with this command, the Prophet brought with him, Al-Hasan and Al-Hussain, because they were the sons of his daughter Fatima, and for this they are his sons. He brought Fatima with him because she represents the women from the members of his House. But why did he bring with him Imam Ali who was neither from the sons nor from the women?
Imam Ali has no place in the verse unless he is included in the word "ourselves." Bringing Imam Ali with him indicates that the Messenger of God considered Imam Ali an extension of his personality. By considering him so, he elevated him above all the Muslims.
The Messenger said on many occasions:

"Ali is from me and I am from him."[3]

Hubshi Ibn Janadah reported that he heard the Messenger of God, saying:

"Ali is from me and I am from him, and no one represents me but Ali."[4]
 

1. [3:61]
فَمَنْ حَاجَّكَ فِيهِ مِن بَعْدِ مَا جَاءَكَ مِنَ الْعِلْمِ فَقُلْ تَعَالَوْا نَدْعُ أَبْنَاءَنَا وَأَبْنَاءَكُمْ وَنِسَاءَنَا وَنِسَاءَكُمْ وَأَنفُسَنَا وَأَنفُسَكُمْ ثُمَّ نَبْتَهِلْ فَنَجْعَل لَّعْنَتَ اللَّـهِ عَلَى الْكَاذِبِينَ
2. [26:23]
قُل لَّا أَسْأَلُكُمْ عَلَيْهِ أَجْرً‌ا إِلَّا الْمَوَدَّةَ فِي الْقُرْ‌بَىٰ
3. «يا رسول اللّه انّک تحبّ عليّاً؟ قال: او ماعلمت انّ عليّاً منّي و انا منه؛احد سال رسول الله(ص):
المناقب، الموفق بن احمد الخوارزمي، قم، جامعه مدرسين، چاپ چهارم،ص 64.
4. قَالَ رَسُولُ اللَّهِ ص عَلِیٌّ مِنِّی وَ أَنَا مِنْ عَلِیٍّ وَ لَا یُؤَدِّی عَنِّی إِلَّا عَلِی علی
Sunan Termezi. V 5. P 300.