Answered by Ustadh Sufyan Qufi
I was wearing slippers; then, some water splashed on some impure ground (which had a small puddle already) and only my feet/slippers. Then I washed my feet (I am certain), but I cannot remember if I washed my slippers (might have but might not have). Then I prayed with soaking wet feet after wudu + my feet obviously touched my clothes, walked around the house with soaking wet feet, etc.
Answer:
In the name of Allah, Most Compassionate, Most Merciful,
“Certainty is not lifted by a doubt.”
[Ibn Nujaym, al-Ashbah wa’l Nadha’ir; Majallat al-Ahkam al-`Adiliyya]
This means that if one is certain about something, such as the validity of our worship, with this being the basic assumption for all human actions, then we will keep assuming it is valid until certain that it was not. Mere possibilities and even likelihoods do not change this.
You were certain that your slippers were filthy. You have doubts about whether you washed them or not. You should thus assume that your slippers are still filthy.
You were certain that you had washed your feet. You cannot be certain on whether the filth on your slippers has transferred to your feet or not. You should thus assume that your feet were pure when you prayed and that your prayers were valid.
I pray this helps.
And Allah knows best.
Wassalam
[Ustadh] Sufyan Qufi
Checked and Approved by Shaykh Faraz Rabbani