Al-Kāfi - Volume 6 > Prayer and Appeal before Allah for a Son
Hadith #4

عَلِيُّ بْنُ إِبْرَاهِيمَ عَنْ أَبِيهِ عَنِ ابْنِ أَبِي عُمَيْرٍ عَنْ بَعْضِ أَصْحَابِهِ قَالَ شَكَا الْأَبْرَشُ الْكَلْبِيُّ إِلَى أَبِي جَعْفَرٍ ( عليه السلام ) أَنَّهُ لَا يُولَدُ لَهُ فَقَالَ لَهُ عَلِّمْنِي شَيْئاً قَالَ اسْتَغْفِرِ اللَّهَ فِي كُلِّ يَوْمٍ أَوْ فِي كُلِّ لَيْلَةٍ مِائَةَ مَرَّةٍ فَإِنَّ اللَّهَ يَقُولُ اسْتَغْفِرُوا رَبَّكُمْ إِنَّهُ كانَ غَفَّاراً إِلَى قَوْلِهِ وَ يُمْدِدْكُمْ بِأَمْوالٍ وَ بَنِينَ .

4. Ali ibn Ibrahim has narrated from his father from ibn abu ‘Umayr from certain persons of his people who has said the following: “Once al-Abrash al-Kalbiy complained before abu Ja‘far, ‘Alayhi al-Salam, and said that he did not have any child and asked him (the Imam) to teach him something. He (the Imam) said, say, ‘I ask forgiveness from Allah, my Lord and return to Him in repentance’ one hundred times every day and every night, because Allah says, ‘Ask forgiveness from your Lord; He is forgiving. ... He helps you by means of your wealth and sons.’” (71:10)