Answered by Shaykh Yusuf Weltch
Question
My whole life when cleaning myself after defecating I would wash the backside first and then wipe afterward until the wipes came back with no traces. Recently I found out you are supposed to wipe first and then wash after. Are all my past prayers invalid?
Answer
In the Name of Allah, the Most Merciful and Compassionate
Your past prayers are valid. Although you should have wiped first and then washed, in the end, the impurity was removed.
Proper Method of Post-Restroom Washing (Istinja’)
Whenever one is washing any impurity away, the proper approach is as follows:
First, minimize the impurity before using water.
Whether after relieving oneself or when cleaning away an impurity elsewhere, it is best to first minimize the impurity by wiping it away or drying (it liquid) up using, for example, a tissue or the like. In case of washing after using the restroom, one wipes first, thus minimizing the amount of impurity.
Second, wash away the impurity with water until one is reasonably sure the impurity is gone
Now that the impurity is minimized, less water/effort is needed to wash the remaining impurity away. Thereafter, if one wants to wipe again, in order to dry the area, they can. However, they should not due so giving in to baseless doubts that some impurity may remain.
Other Materials
Considered looking at the following links for more details on washing impurities and protecting oneself from baseless doubts or misgivings (waswasa):
What is the Best Way to Clean Oneself After Using the Toilet
A Reader on Misgivings (Waswasa)
Hope this helps
Allah knows best
[Shaykh] Yusuf Weltch
Checked and Approved by Shaykh Faraz Rabbani