Those who get waswasa often should also recite the following as much as possible:
أعوذُ باِللهِ مِنَ الشَّيطَانِ الرَّجِيم
“I seek refuge in Allah from the rejected devil.”
لاحول ولا قوة إلا بالله
“There is no power and no strength except with Allah”
اَللَّهُمَّ اجْعَلْ وَسَاوِسَ قَلْبِىْ خَشْيَتَكَ وَ ذِكْرَكَ وَ اجْعَلْ هِمَّتِىْ وَ هَوَايَ فِيْمَا تُحِبُّ وَ تَرْضَى
“O Allah! Convert the whisperings of my heart into Your fear and rememberance and divert my will and courage to the performance of deeds that please You.”
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