اَللَّهُمَّ اجْعَلْنَا مِنَ الْمُسْتَمِعِينَ الْقَوْلَ فَيَتَّبِعُونَ أَحْسَنَهُ
Transliteration
Allahummaj'alna minal-mustami'inal-qawla fa yattabi'una ahsanah
English meaning
O Allah, make us among those who listen to the word and follow the best of it.
When is it recited?
Before the khutbah begins.
Source
Az-Zumar 39/18