This name for the Holy Spirit occurs only once, in parallel to the most common title, Holy Spirit. The Spirit of Jesus (Yeshua‘) prevented or forbade Paul’s missionary team to enter Bithynia, south of the Black Sea. It is unclear why Luke used this name but it is one of many statements that support the doctrine of the Trinity—God the Father, Jesus Christ, and the Holy Spirit are all one. The Holy Spirit is the Spirit of Jesus in the sense that Jesus sent Him after He had ascended to heaven.
Spirit of Jesus in Greek:
To pneuma tou Iēsou
Strong’s Concordance numbers: 4151, 2424
Bible reference: Acts 16:6-7
Paul and his companions traveled throughout the region of Phrygia and Galatia, having been kept by the Holy Spirit from preaching the word in the province of Asia. When they came to the border of Mysia, they tried to enter Bithynia, but the Spirit of Jesus would not allow them to. (Acts 16:6-7 NIV)
There are several variations of this name of the Holy Spirit: Spirit of Jesus Christ, Spirit of Christ, and Spirit of the Lord.