My youngest turned 3 on Wednesday. If he so chose, he could verbally commit to a college right now. Of course, stringing the phrase "verbal commitment" together might be a linguistic challenge for him.
Seriously, there is nothing governing when an athlete may make a verbal committment. I've worked with many athletes who had verbal offers as sophomores and could commit if they chose. There have been cases of basketball phenoms verbally committing in the 8th grade.
Of course, there is nothing binding on either side with these commits.