Authorities say the two got into a dispute while waiting to get into the Community House, run by Central Synagogue, just after 7 a.m.
One homeless man allegedly stabbed another and fled the scene.
The victim, who didn't initially realized he had been stabbed, was taken to Bellevue Hospital with non-life threatening injuries.
The suspect fled westbound on East 55th Street on a bicycle.
He is described as a bald Hispanic man wearing an orange coat.
Anyone with information is urged to contact police.
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