Was God “unmerciful” to Ananias & Sapphira in Acts5:1-10?
The answer is no, as scriptures tell us that God is Merciful:
Merciful and gracious is the Lord (Ps. 111:4)
He saved us, not because of righteous things we had done, but because of his mercy. He saved us through the washing of rebirth and renewal by the Holy Spirit. - Titus3:5
David said to God, “I am in deep distress. Let us fall into the hands of the Lord, for his mercy is great; but do not let me fall into human hands.” - 2Samuel24:14
The Lord is good to all, He has compassion in all He has made. - Psalm145:9
Be merciful just as your Father is merciful. - Luke6:36
But because of His great love for us, God who is rich in mercy - Ephesians2:4
Let us then approach God’s throne of grace with confidence, so that we may receive mercy and find grace to help us in our time of need. - Hebrews4:16
Even Apostle Peter speaks of the great mercy of God:
Praise be to the God and Father of our Lord Jesus Christ! In his great mercy he has given us new birth into a living hope through the resurrection of Jesus Christ from the dead. - 1Peter1:3
We can see from scriptures that our loving God is rich in mercy. we have the teachings of Pope St. John Paul II the Great’s 1980 encyclical Dives in misericordia" and
Pope Francis announced a Year of Mercy with his 2015 Misericordiae vultus.
For more on God Divine Mercy here is a latest article expounding on the coming Divine Mercy Sunday.
Nothing God Won’t Redeem
Merciful and gracious is the Lord (Ps. 111:4), who, out of great love with which He loved us (Eph. 2:4) and [out of] unspeakable goodness, gave us his Only-begotten Son as our Redeemer, so that through the Death and Resurrection of this Son He might open the way to eternal life for the human race, and that the adopted children who received his mercy within his temple might lift up his praise to the ends of the earth. In our times, the Christian faithful in many parts of the world wish to praise the divine mercy in divine worship, particularly in the celebration of the Paschal Mystery, in which God’s loving kindness especially shines forth. Acceding to these wishes, the Supreme Pontiff John Paul II has graciously determined that in the Roman Missal, after the title “Second Sunday of Easter,” there shall henceforth be added the appellation “(or Divine Mercy Sunday),” and has prescribed that the texts assigned for that day in the same Missal and the Liturgy of the Hours of the Roman Rite are always to be used for the liturgical celebration of this Sunday.
Therefore, the answer based on scriptures and the teaching of the Two Popes of our times is our God is Merciful to all mankind as God desires the salvation of all souls.
"This is good, and pleases God our Savior, 4 who wants all people to be saved and to come to a knowledge of the truth."(1Timothy2:3-4)
To answer your specific on the case of Ananias & Sapphira. By the very meaning of the name Ananias it already proclaim that God is merciful or ***"Yahweh Has Been Gracious". ***http://www.abarim-publications.com/Meaning/Ananias.html#.XL46E4kzZdg
It's clear in the passage that the sin of Ananias & Sapphira was "lying" and they did not "blaspheme" the Holy Spirit, lying and blasphemy are two different sins. Lying although a grave matter as written in the 8th commandment but it is not a blasphemy that the scriptures described in Matthew 12:32 like the "unforgivable sin".
Did Ananias & Sapphira committed a "mortal sin"? According to Catholic Church teaching three conditions must be satisfied for it to become a "mortal sin". The answer if we look at the passages is No!, Why? Ananias doesn't know that when he lied to the Apostle he was actually lying also directly to the Holy Spirit as Peter explain it to him. So, the "absence of full knowledge" on the part of Ananias & Sapphira makes their sin not mortal. Although they committed a grave matter with intent but the lack of full knowledge on their part was very clear.
3.Ananias died in the judgement or in the Hands of God. We know that King David stated that it is better to die in the Hand of God rather than hands of man more so in the hands of satan.
"David said to God, “I am in deep distress. Let us fall into the hands of the Lord, for his mercy is great; but do not let me fall into human hands.” - 2Samuel24:14
- Ananias & Sapphira might not know that Satan is the one who deceived them and put malice in their heart to withheld portion of the money which as part of the community vows to share whatever they have in full to meet the needs of all the church members. Satan had infiltrated the heart of Ananias & Sapphira like what he did to Judas as St. Peter stated “Ananias, how is it that Satan has so filled your heart that you have lied to the Holy Spirit ". St. Peter was familiar to the tragic death of Judas when the malice of satan entered his heart that led to his suicide.
Why hath Satan filled thine heart? - The narrative is obviously intended to leave the impression that St. Peter's knowledge of the fact came from a supernatural insight. He had that prophetic gift which gave him insight into the hearts of men, and through this outward show of generous devotion he read the baseness and the lie. And that evil he traced to its fountain-head. Like the sin of Judas (John 13:2; John 13:27), it had in it a malignant subtlety of evil, which implied the perversion of conscience and will just at the moment when they seemed to be, and, it may be, actually were, on the point of attaining a higher perfection than before. The question "why" implies that resistance to the temptation had been possible. Had he resisted the Tempter, he would have fled from him (James 4:7).(Ellicott's Commentary for English Readers)
The Apostle Peter is not only the Chief Shepherd but he is also a priest and Jesus gave Peter the Keys to God's Kingdom. We can see from the passage that Peter not only identifies the "root of sin", he also explain to Ananias what kind of sin that he committed as Ananias thought it was just a simple sin of lying to the Apostles but he was gravely mistaken when Peter indwelt by the Holy Spirit convicted him of his true sins.
The question is, if you were in the feet of Peter whom Jesus entrusted the care of His flock towards their salvation, will you lead a sinner to seek the Mercy of God after explaining the nature of his sin? The answer is yes, as Ananias "heard" what Peter had explained and he gave up his spirit to God, meaning he embraced the judgement of God. Remember Ananias & Sapphira did not commits mortal sin but God acting on His Mercy prevented Satan to fully corrupt their heart like what he did to Judas. Ananias & Sapphira with the help of the priestly powers of St. Peter had accepted the judgement of God and as King David had said it is better to die in the Hand of God. If St. Peter did not intervene immediately, Ananias & Sapphira's heart might be fully corrupted by satan like Judas and we know the possibility for despair and suicide is immenent.
We can see from this passage that God gave His Mercy to Ananias & Sapphira by revealing and convicting them of their sins before it take roots deeply into their heart. The intervention of St. Peter is an act of mercy of God using the priestly powers of Peter to discern the heart of sinners and the power to give absolution of their sins.
As St. Augustine had said in his commentary on this passage:
... There are likewise different opinions among the Fathers, respecting the salvation of Ananias and Saphira. Some are of opinion, that as their fault was great, they died, and perished in their sin. but the ideas we are fond to cherish of the infinite mercy of God, would rather incline us to say, with St. Augustine, "I can believe that God spared them after this life, for his mercy is great ... They were stricken with the scourge of death, that they might not be subject to eternal punishment." (St. Augustine, Serm. cxlviii. olim. 10. et in Parmen.)
George Haydock's Catholic Bible Commentary
- Lastly, we can see from the Book of Acts that God wanted to preserve the unity of the infant church and God would not allow satan to sow disunity by sowing malice in the heart of church members even if it will cause great fear among the followers. Satan was uprooted early by St. Peter to preserve the unity and God used to St. Peter to set an example to the rest of the followers that one must lived by obedience to their vows in community/church life and point out the importance of obeying their leaders as they are indwelt by the power of the Holy Spirit to fulfill the mission of the church towards the salvation of all souls.
All the believers were one in heart and mind. No one claimed that any of their possessions was their own, but they shared everything they had. - Acts4:32
To summarize, God was "Merciful" to Ananias & Sapphira as they both died knowing their sins and they died in the presence of a Priest who have the power to absolve their known sins in the hour of death. As we can see Ananias "heard" and Peter called the attention of Sapphira to "listen" stating his concern for her soul.But, most importantly they both died in the hands of a loving and merciful God who desires their salvation.