Source: The Great Interpretation of Dreams (Ibn Sirin)
Sa'i between Safa and Marwa in a dream indicates striving to fulfill the need of a man and a woman or striving for reconciliation between them.
Source: Perfuming Humanity in the Expression of Dreams (Al-Nabulsi)
Sa'i indicates paying off debt and fulfilling a vow.
Source: Signs in the Science of Expressions (Ibn Shaheen)
Sa'i is interpreted as goodness and blessing. Whoever sees himself performing Sa'i will attain goodness.