This is an acronym for a common salutation in the Christian church meaning "Peace Be With You" which Jesus says to the disciples in the locked room in John 20:19-20.
1) @breyeschow pbwu
2) John 20:19-20 - On the evening of that first day of the week, when the disciples were together, with the doors locked for fear of the Jewish leaders, Jesus came and stood among them and said, "Peace be with you!" After he said this, he showed them his hands and side. The disciples were overjoyed when they saw the Lord.