URDU TRANSLATION:
This narration was telling that the companions were already in the mosque waiting for the prayer but the Holy Prophet(pbuh) was still in JANABAH (a condition which requires the bath after having the sex). The Prophet forgot to have a bath and came to lead the prayer.
This hadith is portraying the image that the companions were more careful about offerring the prayers than the Propeht (pbuh). Astagfirullah!