This quotation comes at the very end of Chapter 11 when Janie and Tea Cake agree to attend the Sunday School picnic together and, in effect, announce their relationship to the town of Eatonville. Tea Cake's words here are a biblical allusion and basically meant to inform Janie that she holds the keys to his heart and that he is completely head-over-heels in love with her.
This is an important statement for Tea Cake to make as we see the beginnings in this chapter of Janie's somewhat recurring doubts of Tea Cake's love and her apprehensions about engaging in a relationship with someone considerably younger. Janie's fears, of course, ultimately prove to be unfounded, but at this point in the novel Janie is unsure of the wisdom of this path. She ultimately acts based upon her heart and not on her mind.
Basically, Tea Cake is telling Janie that she is the woman who controls his hear. Janie feels the age old worries of a woman who is worried that her man, in this case a man considerably younger than her, might not be as interested in her as she is in him. Through this comment, Hurston plays with the repeated biblical allusions and sayings as well as lets the reader and Janie know that she is the person Tea Cake loves. Hope this helps.