In regards to the above question, we will make mention of the verdicts of some of the jurisprudents as under:
According to a well-known view, the jurists say that the duration of breastfeeding is twenty one months.[1] However, some jurists allow breastfeeding for two years and they consider it as recommended. Therefore, there is not any specific difference with the well-known fatwa. Here is a brief explanation:
1. It is recommended to breastfeed a child for two years, if possible.[2]
2. It is recommended to breastfeed a child for twenty one months and it is not appropriate to breastfeed the child for more than two years.[3]
3. The minimum duration of breastfeeding is twenty one months.[4]
As for breastfeeding for more than two years, the fatwa (verdicts) of some jurists are as under:
4. A child should not be breastfed for more than two years, as a measure of precaution.[5]
5. It is permissible to breastfeed a child one or two months more than two years (24 months).[6]
For further information in this regard, see index: "The Solution to the Difference between verse 233 of Sura al-Baqarah and verse 15 of Sura al-Ahqaf, question 6499 (site: 6946).
[1] - Allamah Hilli, Hasan bin Yusuf, Tabsiratul Mu'allemin fi Ahkaam al-Din, pg. 143, Center for Printing and Publication affiliated to Ministry of Islamic Culture and Guidance, Tehran, 1st edition, 1411 A.H.; Tabrizi (r.a); Jawad, New Religious Inquiries (Istiftaat Jadid), vol.1, pg. 372, question 1661, Qom, 1st edition (date unknown).
[2] - Such as: Imam Khomeini, Sayyid Rohullah, Tawzih al-Masail, Research and Editor: Qulipoor Gilani, Muslim, pg. 522, issue 2366, Center for Preparation and Publication of Imam Khomeini's Works, Qom, 1st edition, 1426 A.H.; Fazel Lankarani (r.a), Muhammad, Resalah Tawzih al-Masail, pg. 447, issue 1978 (no date), Qom, 114th edition, 1426 A.H.; Subhani, Ja'far, Resalah Tawzih al-Masail, pg. 464, issue 2132, Imam Sadegh Institute, Qom, 3rd edition, 1429 A.H.
[3] - Such as: Sistani, Imam Khomeini, Tawzih al-Masail (without annotation), researcher and editor: Bani Hashemi Khomeini, Sayyid Muhammad Hussein, vol.2, pg. 512, issue 2491, Islamic Publications Office, Qom, 8th edition, 1424 A.H.
[4] - Tabrizi (r.a), Jawad, New Religious Inquiries (Istiftaat Jadid), vol.1, pg. 372, question 1661, Qom, first edition.
[5] - Shubairi Zanjani, Sayyid Musa, Resalah Tawzih al-Masal, pg. 540, issue 2500, Salsabil Publication, Qom, first edition, 1430 A.H.
[6] - Mohaqiq Helli, Najmuddin Ja'far bin Hasan al-Mukhtasar al-Nafe' fi Fiqh al-Imamiyah, vol.1, pg. 194, Religious Publications Institute, 6th edition, 1418 A.H.