1Pet 4:12-14 Beloved, do not think it strange concerning the fiery trial which is to try you, as though some strange thing happened to you; but rejoice to the extent that you partake of Christ's sufferings, that when His glory is revealed, you may also be glad with exceeding joy. If you are reproached for the name of Christ, blessed are you, for the Spirit of glory and of God rests upon you. On their part He is blasphemed, but on your part He is glorified.
Brethren, when the Lord allows us to go through fiery trials we must rejoice for these trials are for us to glorify Him. In the last days God will allow us to be brought before authority, we too must rejoice for we are counted worthy to be His witness. He wants us to rest in Him so that the Spirit of our Father will be in complete control of our physical bodies to His glory.
Mat 10:18-20 "You will be brought before governors and kings for My sake, as a testimony to them and to the Gentiles. But when they deliver you up, do not worry about how or what you should speak. For it will be given to you in that hour what you should speak; for it is not you who speak, but the Spirit of your Father who speaks in you."
John 14:23 Jesus answered and said to him, "If anyone loves Me, he will keep My word; and My Father will love him, and We will come to him and make Our home with him."
For the Spirit of the Father to dwell in us, we must first love Him by keeping His words. When we keep His words, He will ensure that we will not taste death (feelings, emotions, pains, etc.) in the event of persecutions, tortures and martyrdoms.
4John 8:51-52 "Most assuredly, I say to you, if anyone keeps My word he shall never see death." Then the Jews said to Him, "Now we know that You have a demon! Abraham is dead, and the prophets; and You say, 'If anyone keeps My word he shall never taste death.'"
Martyrdom of Stephen
Mat 16:28 "Assuredly, I say to you, there are some standing here who shall not taste death till they see the Son of Man coming in His kingdom."
Stephen saw our Lord Jesus before the crowd decided to stone him. We can rest assured that Stephen did not feel any pain during the whole period of being stoned. Knowing that his work on earth had finished, he committed his spirit to God and his final witness was kneeling down and calling out loudly to the Father to forgive them of this sin.
Acts 7:55-56, 58-60 But he, being full of the Holy Spirit, gazed into heaven and saw the glory of God, and Jesus standing at the right hand of God, and said, "Look! I see the heavens opened and the Son of Man standing at the right hand of God!"... And they stoned Stephen as he was calling on God and saying, "Lord Jesus, receive my spirit." Then he knelt down and cried out with a loud voice, "Lord, do not charge them with this sin." And when he had said this, he fell asleep.
Martyrdom births sons of God
Heb 2:9 But we see Jesus, who was made a little lower than the angels, for the suffering of death crowned with glory and honor, that He, by the grace of God, might taste death for everyone.
By God's grace our Lord Jesus tasted death for us (who keep His words) so that we do not have to taste the horrific pains, sufferings, and fears of death. We thank God that all those martyred by ISIS did not suffer any pain (no apostasy as the Spirit of the Father was in them), but instead they were rejoicing as their bodies were mutilated.
1Cor 15:55 "O Death, where is your sting? O Hades, where is your victory?"