The phrase "body and soul" is an expression used to describe someone who is completely involved in something or who fully believes in something. When you say someone is with you "body and soul," it means they are committed to you in every way—emotionally and physically.
In more complex sentences, you might say: - "He dedicated himself body and soul to the project, ensuring its success."
While "body and soul" primarily means complete involvement, in different contexts, it can also reflect a deep emotional connection or total immersion in an activity.