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He had no military training, and no skill with the elite weapons of war, but when he saw a battle that needed to be won he didn't hesitate to engage. Against all odds, and armed only with the knowledge of how God had strengthened him before, a sling and a few small stones, David faced a vicious enemy. 1 Samuel 17 gives the account of how David heard the Philistines taunting God and the armies of Israel, how no soldiers were willing to fight the Philistine champion, and how David--depending on the Lord--won the day. Being only a boy, David was met with resistance when he volunteered to fight. King Saul told him he was not able (1 Sam. 17:33).
David's response was brilliant (and helpful): "The Lord who delivered me from the paw of the lion and from the paw of the bear, He will deliver me from the hand of this Philistine" (1 Sam. 17:37). And of course, we know the rest of the story.
David's attitude toward serving God provides an excellent example for us today, especially as we consider spiritual gifts. David lived in a different age, and the Holy Spirit was not operating in exactly the same way--He would temporarily strengthen people for specific tasks, and there is no evidence that He indwelt people then as He does in the church age. Because David wasn't dealing with "spiritual gifts," I use his episode with Goliath as an example, but we have to be careful not to take the analogy too far.
In any case, David was certain he would be able to function successfully in a future endeavor only because of how God provided for him in similar past endeavors. He exhibited no fear in looking forward to the task at hand because of his history with God. But as far as we know, David had no special revelation from God to that point. As far as the Bible reveals, God did not promise David He would deliver him from the lion or the bear--or Goliath. But yet David was confident, and he proclaimed to Goliath, "I come to you in the name of the Lord of hosts, the God of the armies of Israel, whom you have taunted" (17:45).
Let's fast-forward now three thousand years. We know that church-age believers are given spiritual gifts (Rom. 12:6, 1 Cor. 12:4ff, 1 Pet. 4:10). But there is something very odd about these gifts. Nowhere in the Bible is there any indication of specifically how we can know what gift(s) we have been given. All we are told is how the gifts are to be employed--for the common good (1 Cor. 12:7), and in serving one another as good stewards of the manifold grace of God (1 Pet. 4:10). There is simply no data about how we are to identify our spiritual gifts. So where does that leave us? We know He give gifts, and we know we receive them, but we have no way of being certain what gift He has given.
First we must consider that the equipping for good works never comes from spiritual gifts, it comes from the word of God (2 Tim. 3:16-17). If we neglect His word, we simply will not be equipped for His service, for we will not understand how He has designed His gifts to be used and why. Second, we need to recognize that "There are varieties of ministries, and the same Lord. There are varieties of effects, but the same God who works all things in all" (1 Cor. 12:5-6). God has created different gifts and ministries and is capable of using them all however He wishes in order to achieve the result He desires. If we are allowing His word to dwell richly in us (Col. 3:16), then we know we are being equipped for whatever task He has for us, because,
All Scripture is God-breathed and profitable for teaching, for reproof, for correction, for training in righteousness; so that the man of God may be adequate, equipped for every good work. (2 Tim. 3:16-17)
Paul adds, "Whatever you do in word or deed, do all in the name of the Lord Jesus, giving thanks through Him to God the Father" (Col. 3:17). Just as David opposed Goliath in the name of the Lord, in that same way we should pursue all our own activities.
Further, David was able to have confidence in God's future dealings because of His past performance. I suggest that spiritual gifts work the same way. While we have absolutely no way of quantifying what our spiritual gift(s) may be, we can look at how God has used us in the past, giving us particular opportunities and helping us make the most of them. Consequently, we can have confidence in the future that whenever He has a task for us, He has already provided for our equipping through His word (which we must allow to abide in us), that we are as spiritually gifted as He needs us to be in order to engage the task, and that, ultimately, success from His perspective is not brought about by skill and superiority from our perspective.
So we can focus less on trying to identify how He has gifted us, and avoid the paralysis that comes from the predictable uncertainty about our gifts. He simply hasn't told us and offers no mechanism for us to discern such gifts. Instead we are exhorted to do all that we do in the name of Christ--meaning, as if we were representing Him in that activity. If we are thinking, speaking, and working as Christ would, then we know we are on the right track. And rather than looking forward to predict specifically how God might use us, we can prepare diligently and make the most of every opportunity He provides.
When people ask me what spiritual gift(s) God has given me, I tell them I have absolutely no idea--I just try to be faithful with every moment, and seek to accomplish whatever He puts in front of me to accomplish. I am certain of His provision, but beyond what He has revealed I have no need of certainty about how He intends to use me. Some things we can't know, and other things we can. We can know, like David, that whatever we may encounter in the future, God has provided the means for our equipping. Perhaps we can look back one day on a lifetime of service to Him, and discover that He used us repeatedly in particular ways. Perhaps looking back we will be able to see more clearly how He gifted us. But in the meantime, let's look forward with our eyes focused on Him (Heb. 12:2). We can't go wrong if we are following Him.