Here's why:

* Electronegativity: Arsenic and sulfur have relatively similar electronegativity values. The difference in electronegativity between them is not large enough to form an ionic bond.

* Sharing of electrons: Instead of one atom completely gaining or losing electrons, they share electrons to achieve a stable electron configuration.

* Formation of molecules: The covalent bond results in the formation of discrete molecules, like arsenic sulfide (As₂S₃).

Let me know if you have any other questions!