مناسك حج - مكارم شيرازى، ناصر - الصفحة ١٠٨ - Atonements of Ihram
Article ١٨٠- Whenever a person leaves Mustahab Tawaf( even for a necessary reason or not ), then he/ she can continue from the place that he/ she has been, if the person has performed four rounds or not.
Article ١٨١- Sitting has no problem during Tawaf for removing tiredness, but it is obligatory precaution observe the conventional sequence( it means to perform Tawaf without long pauses and in sequential rounds ).
Third: Taharah from impurities.
Article ١٨٢- The body and clothes of a person who performs Tawaf should be pure of any impurities in both obligatory and Mustahab Tawaf, even some of impurities which has been forgiven for prayer( like blood spot smaller than a one dirham coin )should not be on the body or clothes of the person during Tawaf, but if washing the blood of injuries causes strong discomfort, then Tawaf could be performed by that.