I apprehend, in the apostle's mind the phrase 'for my brethren' is connected with both 'pain in my heart' and 'a curse from Christ;' he parenthetically states how far his heart had gone for Israel, and then continues the phrase. This want of strict continuation of grammatical structure is very common with the apostle from the ardour of his style, and only adds force to what he says. He had loved them as much as Moses. (Ex. 32.32.) His pain was continuous: but the wish, 'to be a curse,' was like that of Moses, a moment's earnest appeal, as beside himself.