Urwah bin al-Zubayr (may Allah have mercy on him) said: When Sayyiduna Abu Bakr sent Khalid bin al-Walid (may Allah be pleased with them both) to subdue the apostates, he said: First invite them to Islam, make them aware, strive for their guidance, and accept it from whoever understands and returns. Fight those who disbelieve in Allah after having believed, and whoever accepts Islam, leave his way open; their reckoning is with Allah. And whoever refuses, fight him.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب المرتد / 16849