Source: Tafsir al-Ahlam al-Kabir (Ibn Sirin)
Washing (full body) in a dream indicates repentance, purification, and removal of worry. Washing with cold water indicates healing and wellness. Washing with hot water indicates illness and worry.
Source: Ta'tir al-Anam fi Ta'bir al-Manam (Al-Nabulsi)
Washing indicates payment of debt and relief from distress. For the unmarried, it is marriage, and for the poor, wealth.
Source: Al-Isharat fi Ilm al-Ibarat (Ibn Shahin)
Washing is interpreted as goodness and blessing. Whoever sees himself washing in his clothes indicates his righteousness and chastity.