I had a conversation recently with someone who had received advice about sex at a ministry-wives type event several years ago. As her husband was in ministry, she was advised to make it a priority to have sex with him frequently in order to increase the effectiveness of his ministry. This disturbed me.
I think this is ill-advised for three reasons.
First, it cuts against the self-giving we find in 1 Corinthians 7. One gives oneself to one's husband (or oneself to one's wife), for the other person. Not for their ministry or any other reason. Adding a reason, like bolstering one's husband's ministry makes it less a self-giving and more a transaction. The ministry of the husband (or the wife for that matter), will be best built up because of the strength of the marriage relationship. Engaging in sex and thereby releasing happy chemicals, or adding to a person's sense of significance is all well and good, but for some people this will happen more when they undertake intense physical activity or play a super-charged computer game or some such. I am not certain that the people who pedal this advice would be happy to advise people who aren't invigorated by sex to give it up and go do whatever it is that does make their brains work well. If they did, it would be very disturbing indeed and I would not expect that any Christian would advise other Christians against having sex within a marriage relationship under normal circumstances. It simply cuts against Scripture. Sex isn't for ministry. Sex is for marriage. (And that means marriage isn't for ministry either. Should be obvious, but sometimes it doesn't hurt to make sure.)
Second, the passage in 1 Corinthians specifically allows for the prayer to be the one exception which interrupts a married couple's sex life. But I am reasonably certain that the people who give the advice about sex for ministry would not say that a couple's sex life should be interrupted; indeed, what would logically follow from their argument is that if things are getting rocky in ministry, then more sex is in order. But surely, at least from time to time, prayer might be considered to be beneficial to one's ministry. If the argument is to run consistently, then the advice must also include times where prayer supersedes sex in the relationship. Otherwise it is hard to see how this advice has any relationship with Scripture. But that would seem to cut right against the overweighting of sex that is implied in this advice.
Third, it isn't hard to think of individuals who have not had sex either ever in their entire lives or have ceased to have sex, and who have had what would normally be considered successful ministries. Paul the Apostle springs to mind. He doesn't even see fit to include deprivation of this kind in his list of sufferings in 2 Corinthians (though he does include the anxiety he bears for the churches he knew). Indeed, he argues that singleness (an aspect of which is an absence of sex) benefits ministry in 1 Corinthians 7. We can observe that through church history those without opportunity for sex can have successful ministries, under God. So, Calvin's ministry didn't seriously decline after his wife died. The long list of missionaries in the 19th century who never married, yet faithfully proclaimed the gospel, and saw the impact on many lives. And so on. Sex just isn't necessary for a good ministry.
I don't object to sex. I object to advice about sex that sends women whirling away in despair, trying to figure out how to jump through yet another hoop in order to live the godly Christian life they genuinely want to live. And advice that seems to send them away from their husbands in an area such as sex seems even less palatable.
The Reformers blazed loud and angrily against rules about sex within marriage. Their statement that 'nothing is immoral within marriage' was designed to fend off the interference of the priests who, in the Roman Catholic system, had a huge list of rules about what was right and wrong about marital sex. This would come out in the confessional, where the husband or wife would have to answer quite specific questions about when they had engaged in sex, how they had had sex, for what purpose, and what they had been thinking about at the time. Ultimately there was a third person in every marriage, which helped no-one and was, as the Reformers rightly pointed out, contrary to Scripture.
No, this advice is not going that far down this line, but it is precariously close to drawing up prescriptives which determine when and how sex is part of a marriage and that begins to sound as though it is in the same kind of category in which sat the situation to which the Reformers objected. Sex is something for husbands and wives to talk about together. The wife shouldn't have to feel obligated to fill a particular quota imposed upon her by an external source.
Sex within marriage is not for ministry. Sex within marriage is for the husband and wife of that marriage. Just as I do not listen to my husband for the benefit of his ministry but for his benefit, and as I do not teach our child how to pray for the benefit of my husband's ministry but for the child's benefit - though both activities may well benefit my husband's ministry - so I do not have sex for my husband's ministry, but for and with my husband. I expect it will benefit his ministry because it is a good gift from God and if all is well it should help rather than hinder. But that's true of a very, very large number of things.
Marriage is made for men and women, not for ministry. Ministry is what men and women do, and they do it out of the relational capital in their lives, to which their marriage relationships contribute. It is disappointing to find such a theory, which reflects the concerns of our 21st century sex-addicted society rather than the richer, more substantial relationship concerns of Scripture. Thankfully, Scripture does not have such a mercenary, mechanical and withered view of sex and nor for that matter, of women.