God gives parents assurance in two ways. The first can be called proverbial assurance, and the second kind is grounded in the promises. Suppose husband and wife are talking about their daughter, now only eight-years-old, and mom is worried about whether or not she will "turn out." As her husband tries to reassure her, they keep coming back to the question, "but how do we know?"
The first level of assurance simply concerns her general upbringing -- if we wanted to speak of it crassly, we would talk about "the odds." These are all factors that sociologists could point to and factor in -- intact families, no divorce, good education, loving environment, and so forth. Kids from backgrounds like this do a lot more thriving than kids who don't have any of it. These factors work the same whether we are talking about decent pagans, Mormons, or evangelicals. If kids grow up with mom as a crackhead, and dad an alcoholic, and they receive no education, and spend a lot of time on the streets, it screws them up. This kind of protection for children is a function of common grace, and simple common sense helps us understand it.
I call this level of assurance proverbial because the book of Proverbs does not give us head-for-head commitments and promises. They are proverbs. A little sleep, a little slumber, a little folding of the hands to rest, and sometimes you wind up in Congress banning light bulbs for the rest of us. But as a general rule, hard work leads to wealth, and laziness to poverty, only not in every instance. Sometimes a stitch in time doesn't save nine. Nevertheless, it remains true that it is a worthwhile endeavor to build communities that are kind to children, and which provide them a good place in which to thrive. If we do that, more of them will do that.
But our parents in this example are not content with good odds -- they know other families at church who had children veer off into appalling and self-destructive sin, and what about that? First, it should be recognized that many such "church families" have been actively and effectively undoing the benefit of the general surroundings. Dad had a violent temper, say, which no one at church knew about. Sometimes when a kid goes off the rails, the unpacking of family life afterwards is more revealing than you initially thought it might be.
But suppose that is not the case. The promises I am referring to can only be received by faith. They are not works-based at all, although believing them does result in works. But the works they result in are often simply contributing to the proverbial good environment discussed above. You can plant and water all you want (and you should plant and water, according to the schedule), but God is still the one who gives the increase.
The places where such promises are given are discussed further in Standing on the Promises, and so I want to say just one thing about them here. The promises stand in Scripture to every believing parent in the same relation that the extraordinary promises of answered prayer stand to every Christian. No one should want to say that "whatsoever you ask in My name shall be given" is a proverb. It is a promise. But it is a promise for every Christian that we do not see fulfilled in the lives of every Christian. The reason for the distinction is the presence or absence of faith. Those who pray believing, receive.
What does it mean, then, to pray believing? That is a scriptural study that more of us should undertake, and if we did, we would see more answered prayer. In a similar way, more parents should undertake to study what it means to surrender your children to God.
This is right at the heart of what covenant parents should be doing when they bring their infants to be baptized, and what baptists should be doing when they dedicate their children. It is worth our attention.