CC Madhya 25.115
tāre tiraskaribāre karilā nirdhāraṇe
“Impersonalists do not accept the personal feature of the Supreme Personality of Godhead. The Personality of Godhead is stressed in this verse in order to impress upon them the necessity of accepting Him. Therefore the word ‘aham’ is mentioned three times. To stress something important, one repeats it three times.