"The disciples were to go forth as Christ's witnesses, to declare to the world what they had seen and heard of Him. Their office was the most important to which human beings had ever been called, second only to that of Christ Himself. They were to be workers together with God for the saving of men. As in the Old Testament the twelve patriarchs stood as representatives of Israel, so the twelve apostles stand as representatives of the gospel church. AA 19.1"
"But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto me both in Jerusalem, and in all Judea, and in Samaria, and unto the uttermost part of the earth."
EGW's statement about the disciples being Christ's witnesses aligns with the principle outlined in Acts 1:8.
"During His earthly ministry Christ began to break down the partition wall between Jew and Gentile, and to preach salvation to all mankind. Though He was a Jew, He mingled freely with the Samaritans, setting at nought the Pharisaic customs of the Jews with regard to this despised people. He slept under their roofs, ate at their tables, and taught in their streets. AA 19.2"
"Then saith the woman of Samaria unto him, How is it that thou, being a Jew, askest drink of me, which am a woman of Samaria? for the Jews have no dealings with the Samaritans."
The EGW passage directly references and expands upon the interaction between Jesus and the Samaritan woman, highlighting the breaking down of social barriers. The verse provides the specific example that EGW is elaborating on.
"Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost:"
While not a direct quote, the EGW passage reflects the principle of reaching all people with the gospel, which is the core message of Matthew 28:19. EGW applies this principle to Christ's ministry.
"The Saviour longed to unfold to His disciples the truth regarding the breaking down of the “middle wall of partition” between Israel and the other nations—the truth that “the Gentiles should be fellow heirs” with the Jews and “partakers of His promise in Christ by the gospel.” Ephesians 2:14 ; 3:6 . This truth was revealed in part at the time when He rewarded the faith of the centurion at Capernaum, and also when He preached the gospel to the inhabitants of Sychar. Still more plainly was it revealed on the occasion of His visit to Phoenicia, when He healed the daughter of the Canaanite woman. These experiences helped the disciples to understand that among those whom many regarded as unworthy of salvation, there were souls hungering for the light of truth. AA 19.3"
"For he is our peace, who hath made both one, and hath broken down the middle wall of partition between us;"
Ellen White directly references Ephesians 2:14 in this passage.