The Messenger of Allaah, sallallaahu ʻalayhi wa sallam, said:
“People with black banners will come from the East, among the children of Abbaas. Those coming first of them and those who will come later will be killing people; never help them. Allaah will not help them.On the Day of Judgment, Allaah will put to Hell those who walk under their banner or carry their banner. They are really the most evil creatures of Allaah.They will claim that they are from me. Be careful! I am away from them and they are away from me.Their signs are as follows: They lengthen their hair and wear black clothes. Do not sit in order to support them; do not do business with them in the market; do not show the way to them; do not give water to them; for the people of the sky are disturbed by the takbir (saying 'Allaahu Akbar') that they shout.”
The narrators reported from Abu Umama in the "Saghir" of At-Tabarani. Hadith No: 92 J. Ahadith Vol. 3 no: 8302; R. Ahadith Vol. 1 No-1832. Please interpret the hadith? Please inform me of the authenticity of this hadith?

All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ʻalayhi wa sallam, is His slave and Messenger. 

This hadeeth is very weak, and some scholars even declared it fabricated and false because one of the reporters in its chain of narration was labeled as a liar by hadeeth scholars. Al-Haythami wrote, “This report was narrated by At-Tabaraani. Its chain of narration includes ʻAnbasah ibn Abi Sagheerah, who was accused of lying.” [Manba’ Al-Fawaa'id, 5/245]

Ibn Katheer declared it a fabricated report in his book Jaami’ Al-Masaaneed wa As-Sunan (8/527).

Since the report is fabricated and false, it must be rejected, and you should refrain from relating it or seeking after its interpretation.

Allaah knows best.