Stress was the common denominator in Rabbani's life. Money was always tight, and Rabbani, his parents and three siblings squeezed into a one-bedroom apartment in Flushing. When Rabbani finally made friends, his father disapproved of them and urged him to abide by more conservative Pakistani traditions.
As he searched for answers, Rabbani met Munther Omar Saleh, who was three years older and lived a few buildings away.
It was 2015 and a U.S.-led coalition was beginning to conduct airstrikes against Islamic State, also known as ISIS, after it took control of large swaths of Syria and Iraq. Federal prosecutors would later allege in court documents that Saleh was researching how to build a bomb to carry out a terrorist attack.
Rabbani would later say he knew nothing of Saleh's plans, at least not then. Their friendship deepened and profoundly affected how Rabbani viewed the world.
The charismatic Saleh said Muslims were persecuted by Jews and Christians and suggested that Islamic State was establishing Islam the way the Prophet Muhammad intended.
At first, such talk made Rabbani uncomfortable. But after a few months, the alarm going off inside Rabbani's head slowly faded. For the first time, he would recall years later, Rabbani felt someone accepted him. He didn't want to lose that feeling of belonging.
In 2015, Rabbani and Saleh were often volunteering at Masjid Al-Falah, a mosque in Queens.
Sometimes they spent the night at the mosque, debating different teachings in Islam. They discussed hadiths, written accounts of the Prophet Muhammad's sayings and actions that Muslims use as a source of moral guidance and religious law.
One time, Saleh read a translation of a hadith that he said instructed Muslims to join Islamic State:
"A nation will come from the east with black flags ... if anyone of you finds this nation, then you must join them even if you have to crawl over ice," Rabbani recalled Saleh telling him.