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
ahmad-zuhd:2092 – ʿAbdullāh from my father > Wakīʿ > al-Aʿmash > Khaythamah

[Machine] If you are concerned about the Hereafter, then stay for a while. And if you are occupied with worldly matters, then deal with it. And if you intend to do something good, do not delay it. And when Satan comes to you while you are praying, saying that you are just having a delusion, then prolong it.  

الزهد لأحمد:٢٠٩٢ – حَدَّثَنَا عَبْدُ اللَّهِ حَدَّثَنَا أَبِي حَدَّثَنَا وَكِيعٌ حَدَّثَنَا الْأَعْمَشُ عَنْ خَيْثَمَةَ عَنِ الْحَارِثِ بْنِ قَيْسٍ الْجُعْفِيِّ قَالَ

إِذَا كُنْتَ فِي أَمْرِ الْآخِرَةِ فَتَمَكَّثْ وَإِذَا كُنْتَ فِي أَمْرِ الدُّنْيَا فَتَوَخَّ وَإِذَا هَمَمْتَ بِخَيْرٍ فَلَا تُؤَخِّرْهُ وَإِذَا أَتَاكَ الشَّيْطَانُ وَأَنْتَ تُصَلِّي فَقَالَ إِنَّكَ تُرَائِي فَزِدْهَا طُولًا  

See similar narrations below:

Collected by Nasāʾī's Kubrá
nasai-kubra:11856 – Sūwayd b. Naṣr > ʿAbdullāh > Sufyān > Sulaymān / al-Aʿmash > Khaythamah Wahū Ibn ʿAbd al-Raḥman

[Machine] If you want something good, do not postpone it for tomorrow. And if you are engaged in a matter of the hereafter, stay as long as you can. And if you are in a worldly matter, focus on it. And when you pray, the devil says, "You are being delusional." So, multiply it in length.  

الكبرى للنسائي:١١٨٥٦ – عَنْ سُوَيْدِ بْنِ نَصْرٍ عَنْ عَبْدِ اللهِ عَنْ سُفْيَانَ عَنْ سُلَيْمَانَ وَهُوَ الْأَعْمَشُ عَنْ خَيْثَمَةَ وَهُوَ ابْنُ عَبْدِ الرَّحْمَنِ عَنِ الْحَارِثِ بْنِ قَيْسٍ الْجُعْفِيِّ قَالَ

إِذَا أَرَدْتَ أَمْرًا مِنَ الْخَيْرِ فَلَا تُؤَخِّرْهُ لِغَدٍ وَإِذَا كُنْتَ فِي أَمَرِ آخِرَةٍ فَامْكُثْ مَا اسْتَطَعْتَ وَإِذَا كُنْتَ فِي أَمَرِ الدُّنْيَا فَتَوَجَّهْ وَإِذَا كُنْتَ تُصَلِّي فَقَالَ الشَّيْطَانُ إِنَّكَ تُرَائِي فَزِدْهَا طَوْلًا