Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
suyuti:879a –

“Call upon Allah while being certain of being answered, and know that Allah does not respond to a supplication from the heart of one heedless and occupied by play.” (Using translation from Tirmidhī 3479)   

السيوطي:٨٧٩a –

"ادْعوا الله وأنتم موقنون بالإجابة، واعلَمُوا أن الله لا يستجيبُ دعاءً من قلبٍ غافلٍ لاهٍ" .  

[ت] الترمذي غريب، [ك] الحاكم في المستدرك عن أبى هريرة

See similar narrations below:

Collected by Tirmidhī, Ḥākim
tirmidhi:3479 – ʿAbdullāh b. Muʿāwiyah al-Jumaḥī / a man Ṣāliḥ > Ṣāliḥ al-Murrī > Hishām b. Ḥassān > Muḥammad b. Sīrīn > Abū Hurayrah

“Call upon Allah while being certain of being answered, and know that Allah does not respond to a supplication from the heart of one heedless and occupied by play.”  

الترمذي:٣٤٧٩ – حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مُعَاوِيَةَ الْجُمَحِيُّ وَهُوَ رَجُلٌ صَالِحٌ حَدَّثَنَا صَالِحٌ الْمُرِّيُّ عَنْ هِشَامِ بْنِ حَسَّانَ عَنْ مُحَمَّدِ بْنِ سِيرِينَ عَنْ أَبِي هُرَيْرَةَ قَالَ

قَالَ رَسُولُ اللَّهِ ﷺ ادْعُوا اللَّهَ وَأَنْتُمْ مُوقِنُونَ بِالإِجَابَةِ وَاعْلَمُوا أَنَّ اللَّهَ لاَ يَسْتَجِيبُ دُعَاءً مِنْ قَلْبٍ غَافِلٍ لاَهٍ  

قَالَ أَبُو عِيسَى هَذَا حَدِيثٌ غَرِيبٌ لاَ نَعْرِفُهُ إِلاَّ مِنْ هَذَا الْوَجْهِ سَمِعْتُ عَبَّاسًا الْعَنْبَرِيَّ يَقُولُ اكْتُبُوا عَنْ عَبْدِ اللَّهِ بْنِ مُعَاوِيَةَ الْجُمَحِيِّ فَإِنَّهُ ثِقَةٌ
hakim:1817 – ʿAbdān b. Yazīd al-Daqqāq Bihamdān > Ibrāhīm b. al-Ḥusayn b. Dīzīl > ʿAffān b. Muslim And Mūsá b. Ismāʿīl > Ṣāliḥ al-Murrī > Hishām b. Ḥassān > Muḥammad b. Sīrīn > Abū Hurayrah

“Call upon Allah while being certain of being answered, and know that Allah does not respond to a supplication from the heart of one heedless and occupied by play.” (Using translation from Tirmidhī 3479)   

الحاكم:١٨١٧ – أَخْبَرَنَا عَبْدَانُ بْنُ يَزِيدَ الدَّقَّاقُ بِهَمْدَانَ ثنا إِبْرَاهِيمُ بْنُ الْحُسَيْنِ بْنِ دِيزِيلَ ثنا عَفَّانُ بْنُ مُسْلِمٍ وَمُوسَى بْنُ إِسْمَاعِيلَ قَالَا ثنا صَالِحٌ الْمُرِّيُّ عَنْ هِشَامِ بْنِ حَسَّانَ عَنْ مُحَمَّدِ بْنِ سِيرِينَ عَنْ أَبِي هُرَيْرَةَ

عَنِ النَّبِيِّ ﷺ قَالَ «ادْعُوا اللَّهَ وَأَنْتُمْ مُوقِنُونَ بِالْإِجَابَةِ وَاعْلَمُوا أَنَّ اللَّهَ لَا يَقْبَلُ دُعَاءً مِنْ قَلْبٍ غَافِلٍ لَاهٍ»  

هَذَا حَدِيثٌ مُسْتَقِيمُ الْإِسْنَادِ تَفَرَّدَ بِهِ صَالِحٌ الْمُرِّيُّ وَهُوَ أَحَدُ زُهَّادِ أَهْلِ الْبَصْرَةِ وَلَمْ يُخَرِّجَاهُ