Explanation

Uthman Ibn Madhoon died on the 3rd of Sha'ban in the 3rd year of Hijrah.

The first companion buried in Al-Baqi was Uthman Ibn Madhoon 

He was considered the first companion of Muhammad (PBUH) from the Muhajirun to be buried in the cemetery.

while

Hazrat Khadija (RA) was the only Ummul Momineen who was not buried in Jannatul Baqi.

ND21-2-2023