To plead with someone for something. This phrase often suggests a certain intensity or desperation from the speaker. A noun can be used between "beg" and "of." Oh, please come with me tonight, I beg of you. I can't possibly go alone. Can I beg a few dollars of you? I forgot my wallet at home today.
beg something of someone
to request earnestly that someone do something or grant something. Please help me. I beg it of you. She begged a favor of Max.
beg of someone
to request earnestly of someone. (Usually added to a request.) Please help me. I beg of you. I beg of you to help me.