The journal entry to recognize $1000 of commissions earned but not collected would include a debit to commissions

Commissions earned but not yet collected are an asset. You want to debit some type of Receivable account. This could be something like Commissions Receivable. The credit will be an income account.

Commissions Receivable - 1000 (debit)
Commissions revenue - 1000 (credit)