While I cannot give a scripture with that particular promise it is evident that this is what occurred. The disciples cowered in fear behind locked doors. Jesus came to them and showed them that He had power over life and death- even them some still did not understand and some doubted. But then something marvelous happened- the day of Pentecost. At the outpouring of the Holy Spirit these timid people changed from scared little children to lions for Christ. This man Peter who denied Christ rather than suffer for Him (as history records) beseeching the Romans to crucify him upside down as he did not count himself worthy of the same death that Jesus faced. That the joy of the Lord became their strength there is no doubt. They found great satisfaction and joy in laying down their very lives for Jesus and oft went away rejoicing that they were worthy to be beaten for His Name. The disciples were know to sing as they were in imprisoned, tortured and killed and this was one of the things that brought many to Christ. As the Christians in the coliseum (spl?) used to sing as they were thrown to the lions- tonight we will be with Jesus in paradise and you will still be stuck here.