Speaking ahead of Ajax's Dutch Cup game against Utrecht on Wednesday, Ten Hag also said the incident has affected the whole dressing room but Promes could still return to action on Sunday against ADO Den Haag in the Eredivisie.
"First of all, it hits us, it hits me," he said. "This affects the entire dressing room. I spoke to [Promes] and he is now doing well. I haven't spoken to him that extensively yet, just by phone. Tomorrow I will talk with him about it. He said to me he didn't do anything. In this country you are innocent until proven otherwise. We stand behind him including the entire dressing room.
"You are always an Ajax player, also outside the field. We will have that conversation with him. Our managing board has already spoken to him.
"I don't have to forgive him, because he didn't do anything. So it is certainly possible that Promes will be back in the squad on Sunday. Like I said, as long as he's innocent, he's our player. We are happy with him."
Reports in the Netherlands on Sunday claimed Promes had been arrested in connection to an alleged stabbing that took place in July.
Dutch newspaper De Telegraaf reported a stabbing happened in Abcoude, just south of Amsterdam, at a family reunion hosted by Promes on the premises of a company he owns. The report added the player got into a fight with one of his relatives there and stabbed him.
Police did not confirm the identity of the suspect but said a 28-year-old from Amsterdam had been arrested in connection with the alleged incident. Police said the man stabbed, who was seriously injured in the incident, pressed charges last month.