Summary: If God killed every Christian who lied, the churches would be empty. This does not excuse lying, but it does acknowledge our fallibility. The message is a study of one couple that attempted to deceive God and what He did about their deceit.
“A man named Ananias, with his wife Sapphira, sold a piece of property, and with his wife’s knowledge he kept back for himself some of the proceeds and brought only a part of it and laid it at the apostles’ feet. But Peter said, ‘Ananias, why has Satan filled your heart to lie to the Holy Spirit and to keep back for yourself part of the proceeds of the land? While it remained unsold, did it not remain your own? And after it was sold, was it not at your disposal? Why is it that you have contrived this deed in your heart? You have not lied to man but to God.’ When Ananias heard these words, he fell down and breathed his last. And great fear came upon all who heard of it. The young men rose and wrapped him up and carried him out and buried him.
“After an interval of about three hours his wife came in, not knowing what had happened. And Peter said to her, ‘Tell me whether you sold the land for so much.’ And she said, ‘Yes, for so much.’ But Peter said to her, ‘How is it that you have agreed together to test the Spirit of the Lord? Behold, the feet of those who have buried your husband are at the door, and they will carry you out.’ Immediately she fell down at his feet and breathed her last. When the young men came in they found her dead, and they carried her out and buried her beside her husband.”
f God killed every Christian who lied, the churches would be empty. This does not excuse lying, but it does acknowledge our fallibility. We know we are to be truthful in our speech and in our actions. However, we fail miserably to live up to what we know to be correct. Nevertheless, there is a point at which God does finally say, “Enough!” Knowing this to be true, Christians need to learn restraint. We need to hear the words of Jesus, who taught us, “Let what you say be simply ‘Yes’ or ‘No’; anything more than this comes from evil” [MATTHEW 5:37 (quickview) ].
In fact, God does not kill individuals because they lie. There is, as you suspect, a caveat to be pronounced. Lying to the Holy Spirit invites immediate and severe judgement—and the more so when the lying revolves around idolatry. Idolatry? Where is the idolatry in this pericope? It is a legitimate question. Think of a few portions of the Word and the idolatry becomes apparent.
There are several verses that we should hold in mind as we prepare to study why God would kill this husband and his wife. In order to prepare ourselves, I invite you to join me in looking at two verses in the Letter that the Apostle Paul wrote to the Colossian congregation. “Put to death what belongs to your worldly nature: sexual immorality, impurity, lust, evil desire, and greed, which is idolatry. Because of these, God’s wrath comes on the disobedient” [COLOSSIANS 3:5 (quickview) , 6 HCSB].
Again, consider what Paul has written in EPHESIANS 5:3-7 (quickview)  as translated in the NET BIBLE. “Among you there must not be either sexual immorality, impurity of any kind, or greed, as these are not fitting for the saints. Neither should there be vulgar speech, foolish talk, or coarse jesting—all of which are out of character—but rather thanksgiving. For you can be confident of this one thing: that no person who is immoral, impure, or greedy (such a person is an idolater) has any inheritance in the kingdom of Christ and God.