Assalamualaikum w.b.t. Is it true there is a hadith which narrated that water flowed from the fingers of Rasullullah PBUH and the companions used it to perform ablution?
Alhamdulillah, praise and gratitude to Allah SWT for His countless blessings for us all. Praise and salutations to our beloved Prophet Muhammad PBUH, his family, companions and all those who follow his footsteps until the Last Day.
According to the above question, it is as narrated by Anas bin Malik RA, he said:
أَنَّ النَّبِيَّ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ دَعَا بِإِنَاءٍ مِنْ مَاءٍ، فَأُتِيَ بِقَدَحٍ رَحْرَاحٍ، فِيهِ شَيْءٌ مِنْ مَاءٍ، فَوَضَعَ أَصَابِعَهُ فِيهِ. قَالَ أَنَسٌ: فَجَعَلْتُ أَنْظُرُ إِلَى المَاءِ يَنْبُعُ مِنْ بَيْنِ أَصَابِعِهِ. قَالَ أَنَسٌ: فَحَزَرْتُ مَنْ تَوَضَّأَ، مَا بَيْنَ السَّبْعِينَ إِلَى الثَّمَانِينَ.
“The Prophet (ﷺ) asked for water and a tumbler with a broad base and no so deep, containing a small quantity of water, was brought to him whereby he put his fingers in it.” Anas further said, ‘ noticed the water springing out from amongst his fingers.” Anas added, ‘ estimated that the people who performed ablution with it numbered between seventy to eighty.”
This hadith shows the miracle of Rasullullah PBUH. Anas bin Malik RA further detailed the incident in another narration where he said:
رَأَيْتُ رَسُولَ اللَّهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ وَحَانَتْ صَلاَةُ العَصْرِ، فَالْتُمِسَ الوَضُوءُ فَلَمْ يَجِدُوهُ، فَأُتِيَ رَسُولُ اللَّهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ بِوَضُوءٍ، فَوَضَعَ رَسُولُ اللَّهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ يَدَهُ فِي ذَلِكَ الإِنَاءِ، فَأَمَرَ النَّاسَ أَنْ يَتَوَضَّئُوا مِنْهُ، “فَرَأَيْتُ المَاءَ يَنْبُعُ مِنْ تَحْتِ أَصَابِعِهِ، فَتَوَضَّأَ النَّاسُ حَتَّى تَوَضَّئُوا مِنْ عِنْدِ آخِرِهِمْ
“I saw Allah’s Messenger (ﷺ) at the ‘time when the `Asr prayer was due. Then the people were searching for water for ablution but they could not find any. Then some water was brought to Allah’s Messenger (ﷺ) and he placed his hand in the pot and ordered the people to perform the ablution with the water. I saw water flowing from underneath his fingers and the people started performing the ablution till all of them did it.” 
From Jabir bin Abdullah RA, he said:
عَطِشَ النَّاسُ يَوْمَ الحُدَيْبِيَةِ وَالنَّبِيُّ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ بَيْنَ يَدَيْهِ رِكْوَةٌ فَتَوَضَّأَ، فَجَهِشَ النَّاسُ نَحْوَهُ، فَقَالَ: «مَا لَكُمْ؟» قَالُوا: لَيْسَ عِنْدَنَا مَاءٌ نَتَوَضَّأُ وَلاَ نَشْرَبُ إِلَّا مَا بَيْنَ يَدَيْكَ، فَوَضَعَ يَدَهُ فِي الرِّكْوَةِ، فَجَعَلَ المَاءُ يَثُورُ بَيْنَ أَصَابِعِهِ، كَأَمْثَالِ العُيُونِ، فَشَرِبْنَا وَتَوَضَّأْنَا قُلْتُ: كَمْ كُنْتُمْ؟ قَالَ: لَوْ كُنَّا مِائَةَ أَلْفٍ لَكَفَانَا، كُنَّا خَمْسَ عَشْرَةَ مِائَةً
“The people became very thirsty on the day of Al-Hudaibiya (Treaty). A small pot containing some water was in front of the Prophet (ﷺ) and when he had finished the ablution, the people rushed toward him. He asked, ‘What is wrong with you?’ They replied, ‘We have no water either for performing ablution or for drinking except what is present in front of you.’ So, he placed his hand in that pot and the water started flowing among his fingers like springs. We all drank and performed ablution (from it).” I asked Jabir, “How many were you?” he replied, “Even if we had been one-hundred-thousand, it would have been sufficient for us, but we were fifteen-hundred.” 
Qadhi Iyadh said: “This story is narrated by numerous thiqah people and the sanad reaches to the companions. And this incident happened in places some of them gathered, events places, and the place where armies are gathered. None contradict the narrators. It is so, that this incident became additional support of the prophethood of the Prophet PBUH.” 
Ibn Abd al-Barr cited the opinion Imam al-Muzani, saying: “The flowing of water from the fingers of Rasullullah PBUH is a greater miracle than the water flowing from a rock that has been hit by the staph of Prophet Moses RA. The reason is water flowing from rocks is well-known, different from water flowing from flesh and blood.” 
In conclusion, we state that the story of water flowing from the fingers of Rasullullah PBUH and the companions using the water to perform ablution and drink is true and sahih as recorded in Sahih al-Bukhari and Muslim as well as narrated by numerous thiqah narrators. This shows the miracle of Rasullullah PBUH and among the ‘Alamah al-Nubuwwah (signs of his prophethood) of the Prophet PBUH.
Lastly, may Allah SWT grant us all understanding in this religion. Amin.
 Narrated by al-Bukhari (3573) and Muslim (2279)
 Narrated by al-Bukhari (3576), and Muslim (1856)
 See Fath al-Bari, 6/676
 Ibid, 6/677