It is narrated from Amir bin Sa'd bin Abi Waqqas (may Allah have mercy on him) that Usamah bin Zayd (may Allah be pleased with them both) informed his father, Sa'd bin Abi Waqqas (may Allah be pleased with him), saying that a man came to the Prophet (peace and blessings be upon him) and said: I practise withdrawal ('azl) with my wife. He (peace and blessings be upon him) said to him: "Why do you do that?" He said: Out of concern for her child. He (peace and blessings be upon him) said: "If that were so, it would have harmed the Persians and the Romans," meaning: it did not harm the Persians and the Romans.
Muslim (may Allah have mercy on him) recorded it in his Sahih from Ibn Numayr and others, from al-Muqri'.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الرضاع / 15685