According to Michael McDonald, this was based on the original Hebrew name for God (Yahweh), and was originally called "Yahweh Be There." The title was James Ingram's idea: "We were talking about how to say G-d will be there without scaring most of the audience away." It was co-written and produced by Quincy Jones (who does the African style sounds in the song) and Rod Temperton, who later wrote "Sweet Freedom" for McDonald (the theme from Running Scared).
This won a Grammy for Best R&B Performance by a Duo or Group with Vocal.
Michael McDonald has sung this solo over the years. It was even an in-joke in the film The 40 Year Old Virgin in which one of the characters sees a DVD of the McDonald Soundstage production playing in a store and says, "If I hear Ya Mo B There one more time I'm gonna 'ya mo' burn this place!" The song isn't even on the DVD.
Suggestion credit: Sara - Silver Spring, MD, for all above