All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
Being in a state of ritual purity is a prerequisite for the validity of tawaf. When it is a prerequisite, it means that one's tawaf is invalid without it. This is the opinion of the majority of scholars.
Thus, when one's wudhoo’ (ablution) is broken during his tawaf and he proceeds without renewing, his tawaf becomes invalid. He is required to make up for that tawaf as long as he is still in Mecca. In case he returned to his country, he is not required to make up for the tawaf. Rather, he is required to slaughter a sheep and distribute it among the poor of the Sacred Precincts of Mecca. In Al-Mughni, Ibn Qudaamah said, "According to Ahmad, being in a state of ritual purity is not a prerequisite for tawaf. One is required to make up for tawaf as long as he is still in Mecca. In case he has returned home, he is required to slaughter (a sheep) as compensation."
Allaah Knows best.