Translation
(14) Fasting (Kitab Al-Siyam)
كتاب الصوم
(769) Chapter: Whoever Said That It Applies To The Elderly And Pregnant
(3) باب مَنْ قَالَ هِيَ مُثْبَتَةٌ لِلشَّيْخِ وَالْحُبْلَى
Sunan Abi Dawud 2318 

Narrated Abdullah ibn Abbas:

Explaining the verse; "For those who can do it (with hard-ship) is a ransom, the feeding of one, that is indigent," he said: This was a concession granted to the aged man and woman who were able to keep fast; they were allowed to leave the fast and instead feed an indigent person for each fast; (and a concession) to pregnant and suckling woman when they apprehended harm (to themselves).

حَدَّثَنَا ابْنُ الْمُثَنَّى، حَدَّثَنَا ابْنُ أَبِي عَدِيٍّ، عَنْ سَعِيدٍ، عَنْ قَتَادَةَ، عَنْ عَزْرَةَ، عَنْ سَعِيدِ بْنِ جُبَيْرٍ، عَنِ ابْنِ عَبَّاسٍ، ‏{‏ وَعَلَى الَّذِينَ يُطِيقُونَهُ فِدْيَةٌ طَعَامُ مِسْكِينٍ ‏}‏ قَالَ كَانَتْ رُخْصَةً لِلشَّيْخِ الْكَبِيرِ وَالْمَرْأَةِ الْكَبِيرَةِ وَهُمَا يُطِيقَانِ الصِّيَامَ أَنْ يُفْطِرَا وَيُطْعِمَا مَكَانَ كُلِّ يَوْمٍ مِسْكِينًا وَالْحُبْلَى وَالْمُرْضِعُ إِذَا خَافَتَا - قَالَ أَبُو دَاوُدَ يَعْنِي عَلَى أَوْلاَدِهِمَا - أَفْطَرَتَا وَأَطْعَمَتَا ‏.‏
Grade :  Shadh (Al-Albani) شاذ  (الألباني)حكم :
Reference : Sunan Abi Dawud 2318
In-book reference : Book 14, Hadith 6
English translation : Book 13, Hadith 2311