عَنِ الْحَسَن أَنَّ أَبَا الدَّرْدَاء كَانَ يَقُولُ : جِدُّوا فِي الدُّعَاءِ فَأِنَّهُ مَنْ يُكْثِرُ قَرْعَ الْبَابِ يُوشِكُ أَن يُفْتَحَ لَهُ

Al-Hasan reported that Abu Darda رضي الله تعالى عنه used to say:

Be diligent in your supplication, for whoever keeps knocking at the door is likely to have it opened for him