Third textbook example: genitive

The Rule of the Muʿrab: Visible and Estimated Case

مَرَرْتُ بِزَيْدٍ
Translation: I passed by Zayd.

Parsing
مَرَرْتُ: past-tense verb, whose attached تُ is its subject.
بِـ: preposition; in this context, “by/past.”
زَيْدٍ: genitive noun, with an overt kasra.

Important
The noun is genitive because of the preposition «بِـ», not because the past verb alone directly assigns genitive case.