وَيُكْرَهُ أَنْ يُقَدِّمَ الْإِنْسَانُ ثِقْلَهُ إِلَى مَكَّةَ وَيُقِيمَ بِهَا حَتَّى يَرْمِيَ
Translation: It is disliked for a person to send his baggage to Makkah and stay there before performing the remaining stoning.
Thiqalahu is his travel baggage or load. Al-Quduri dislikes sending the luggage ahead to Makkah and residing there while the required stoning in Mina is still outstanding. The pronoun in bihā refers back to Makkah.
The point is not to let preparations for departure displace attention to the remaining rites. Modern collective luggage transport may involve different necessities; such cases should follow qualified guidance and the pilgrimage authorities' arrangements.