يَا رَجُلًا، خُذْ بِيَدِي!
Translation: O some man! Hold my hand!
يَا: particle.
رَجُلًا: unspecified indefinite vocative, accusative with tanwīn.
خُذْ: imperative built on sukūn, hidden “you” subject.
بِ: preposition.
يَدِي: “my hand”, genitive after bi, with possessive yāʾ.
The addressee is accusative, whereas “my hand” is governed by the preposition.