The attack happened just after 7 am at the temple on South Cherry Avenue as the victim, Piara Singh, was walking down the road, The Fresno Bee reported.
Gilbert Garcia, who has a record of arrests in the Fresno area, was arrested about 8 am Sunday in a rural neighbourhood a half-mile away, the Bee reported citing police chief Jerry Dyer.
As he was being detained, Garcia uttered a threat in an outburst. Dyer said police are investigating the threat, but he declined to say what was said.
"We need to determine if the threat was made with intent, or was he spouting off," the chief said.
Dyer and officials from the US Attorney's Office in Fresno met with more than 100 people at the Sikh gurdwara Tuesday evening to discuss the attack.
Piara Singh was reportedly approached by a man in his late 20s or early 30s who was riding a bicycle and armed with a steel rod.
Without saying a word, the attacker beat Singh in the head and body. Singh is hospitalized with head wounds, broken ribs and lung lacerations.
Temple officials cited by the Bee said the attack was not a robbery and that Singh had never seen the man before.
If the attack is determined to be a hate crime, federal charges could be filed, Mark Cullers, chief of the US Attorney's Office in Fresno was quoted as saying by the Bee. That could be in addition to any state charges filed against the assailant, he said.