Be fruitful and multiply.

...young couples should keep God's commandments without deviation and have many children. Those who refrain from having more than two children are transgressors of God's commandment which says Be fruitful, and multiply (Gen. 1:28), since they being two individuals bring two children into the world and do not increase the population. Increase, that is, from zero population. The Lord is clear, and His commandment in this case is twofold. First He said 'be fruitful' and then He said 'multiply.' So, whichever couples have four children fulfill the first commandment, that is, 'be fruitful.' Whichever ones, again, have five or more please God, because they fulfill both of His commandments, both to be 'fruitful' and to 'multiply.'
Fr. Anthimos of St. Anne's Skete