This hadith proves the special status of Imam Husayn in Islam. It is not a little thing that Prophet (pbuh) said “I am from Husayn”. It clearly proves that the Prophet gave the guarantee about Imam Husayn that whatever the Imam will say or act upon that action will be considered as Holy Prophet's action!
English Translation:

Sayyidina Ya’la ibn Murrah reported that Allah’s Messenger said,

“Husayn is from me and l am from Husayn. Allah loves that person who loves Husayn. Husayn is a grandson among grandsons.”

This is graded as Hassan Hadith

Please read another narration

English Narration:

Sayyidina Ibn Abbas (RA) narrated: Allah Messenger (SAW) had carried Husayn ibn Ali on his shoulder. A man commented,

“What an excellent conveyance, you are riding. 0 young boy!”

The Prophet said, “He is an excellent rider!”

The Holy Prophet told the status of Imam Husayn to that man and to the world that I am blessed with such a great rider on me who is my grandson Husayn.

This is graded as Hassan Hadith