What does Suhrawardi mean by 'the caves of the mountains of Banu'l-Akhyaf'?

Suhrawardi, an Islamic and Persian sage wrote: >The party of God will become divine, will praise God, will detach themselves and pass through the caves of the two mountains of Banu'l-Akhyaf to the two mountains of the Lesser Orient and Greater Orient, reaching the Gate of Gates. **Q. What does Suhrawardi mean by the "caves of Banu'l-Akhyaf"?**