What is the ruling if a scholar issues a fatwa on an issue with one opinion, and then issues a fatwa on the same issue with another opinion?
Machine translationRead the Arabic original
The questioner : Which sunnah corresponds to the word of Allah to a scholar? And we remain silent about this issue. What is the solution?
The Shaykh : What informed us that he left it due to negligence?
The questioner : I am a transmitter.
The Shaykh : After that, he said, for example, that it is haram.
The questioner : In Egypt, another one.
The Shaykh : That means he has two opinions on the issue, and there is no objection to that. A person may have two opinions on an issue, either because he was negligent regarding the evidence in the first opinion and it became clear to him later, or because he acquired additional knowledge. For this reason, we find that the Imams have multiple opinions. Imam Ahmad, the Imam of the Imams (may Allah have mercy on him), may have four or five opinions on a single issue. Imam al-Shafi'i is likewise; there is disagreement in his school between the new madhhab and the old madhhab.
The Shaykh : What informed us that he left it due to negligence?
The questioner : I am a transmitter.
The Shaykh : After that, he said, for example, that it is haram.
The questioner : In Egypt, another one.
The Shaykh : That means he has two opinions on the issue, and there is no objection to that. A person may have two opinions on an issue, either because he was negligent regarding the evidence in the first opinion and it became clear to him later, or because he acquired additional knowledge. For this reason, we find that the Imams have multiple opinions. Imam Ahmad, the Imam of the Imams (may Allah have mercy on him), may have four or five opinions on a single issue. Imam al-Shafi'i is likewise; there is disagreement in his school between the new madhhab and the old madhhab.
Source
قناة «فضيلة الشيخ محمد بن صالح العثيمين»، 4110 - 4600 ما الحكم لو أن عالماً أفتى في مسألة بقول ثم أفتى في المسألة نفسها بقول أخر؟ ابن عثيمين — youtube.com
The Arabic text is a machine transcription of the audio recording.