Purity: Doubt About Timing of Wudu Invalidity After Prayers

Practical Laws of Islam as per the teachings of Ayatullah Sistani

Ruling 305:

If a person realises after prayers that his wuḍūʾ has become void but doubts whether his wuḍūʾ became void before or after prayers, the prayers performed by him are valid.

-Ayatullah Sistani, Practical Laws of Islam, Purification (Taharah)