Hakim bin Umayr (may Allah have mercy on him) said that Sayyiduna Umar (may Allah be pleased with him) wrote to Sayyiduna Umayr bin Sa'd al-Ansari (may Allah be pleased with him) and to his governors that they should not carry out a prescribed punishment (hadd) on any of the Muslims in the abode of war (dar al-harb) until they come out to the land of peace treaty.
Imam al-Shafi'i (may Allah have mercy on him) said: What is reported from Sayyiduna Umar (may Allah be pleased with him) is munkar (objectionable), and he (Abu Yusuf) himself finds fault with taking as evidence a hadith that is not established, yet he says: 'A shaykh narrated to us' - and who is this shaykh? And he says: 'Makhul from Zayd bin Thabit,' while Makhul never saw Zayd bin Thabit. Imam al-Shafi'i also said: As for his saying that he would join the polytheists, if he joins them, that is all the more wretched for him; and whoever abandons the prescribed punishment for fear that the one punished will join the lands of the polytheists would have to abandon it in the coastal regions of the Muslims and their frontier posts that adjoin the lands of war (bilad al-harb).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18226