Allah, the Blessed and Exalted, says: "Then marry those of the women who please you, two, three or four; but if you fear that you will not be just, then (marry only) one, or those your right hands possess. That is more likely to keep you from (being burdened with a large household)." [Surah al-Nisa': 3]
Imam al-Shafi'i (may Allah have mercy on him) said: "(That is,) when a man restricts himself to one wife, the number of those whom you support will not become large, even though Allah Almighty has permitted him more than that."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الرضاع / Q15688