be om is like 'ask for' in English. You typically ask for nouns that you want to get: Jag ber om vatten 'I'm asking for water'. But when you ask someone to do something, it's just ber, without a preposition. If you add om here, you need to have a clause after it. Jag ber om att han ska prata långsamt 'I ask for him to speak slowly'.