Muslims have no less confidence of their having eternal life based upon their reading of the Qur’an than you do based upon your severe lack of understanding of the Bible.
Obviously, it's you who has a severe lack of understanding of the Bible. What understanding of 1 John 5:13 and I severely lacking? In 1 John 5:13 we read - These things I have written to you who
believe in the name of the Son of God, that you may
know that you have eternal life, and that you may continue to believe in the name of the Son of God. Are you calling God a liar?
Can a Muslim know for sure he has eternal life? How can he? I know I do as a Christian precisely because eternal life is not based on the merits of my works. My assurance of salvation is found in Jesus Christ, which is not a misguided assurance based on works (or martyrdom), yet for the Islamic system of works that, at best, only provides the possibility of salvation if they have been sincere enough and if they have done enough good works.
Consider the following verses from the Qur'an in regards to salvation and works.
"Then those whose balance (of good deeds) is heavy, they will be successful. But those whose balance is light, will be those who have lost their souls; in hell will they abide," (23:102-103).
"And We set a just balance for the Day of Resurrection so that no soul is wronged in aught. Though it be of the weight of a grain of mustard seed, We bring it. And We suffice for reckoners," (21:47).
"They are those who deny the Signs of their Lord and the fact of their having to meet Him (in the Hereafter): vain will be their works, nor shall We, on the Day of Judgment, give them any weight," (online Qur'an, 18:105).
Does the Islamic system of salvation really provide assurance of salvation for Muslims? As a Christian, I don't see how anyone in Islam can have security and honest expectation of obtaining eternal life, but they may have misguided hopes.
Is it not audaciously and sinfully arrogant for anyone to think that they can understand the Greek New Testament Scriptures without being able to read them, but that no one could understand them until a renegade Roman Catholic politician came upon the scene with his cronies and “revealed” the true meaning of the Bible?
In 1 Corinthians 2:11-14, we read - 11 For what man knows the things of a man except the spirit of the man which is in him? Even so no one knows the things of God except the Spirit of God. 12 Now we have received,
not the spirit of the world, but the Spirit who is from God, that we might know the things that have been freely given to us by God. 13 These things we also speak,
not in words which man's wisdom teaches but which the Holy Spirit teaches, comparing spiritual things with spiritual. 14 But the
natural man does not receive the things of the Spirit of God, for they are foolishness to him; nor can he know them, because they are spiritually discerned.