The following is part of an article from “got.questions” on the passage in John 19 regarding Jesus 3rd saying on the cross.

When Jesus was on the cross, both the apostle John and Mary the mother of Jesus stood nearby. In John 19:26–27 we read, “When Jesus saw his mother there, and the disciple whom he loved standing nearby, he said to her, ‘Woman, here is your son,’ and to the disciple, ‘Here is your mother.’ From that time on, this disciple took her into his home.”

Mary was probably a widow at this point in her life. Though she had other sons, Jesus chose John to provide care for Mary after His death. Why? Jesus’ brothers  did not become believers until after His resurrection (John 7:5). Further, Jesus’ brothers were not present at His crucifixion. Jesus was entrusting Mary to John,  who was a believer and was present.

As the oldest son in His family, Jesus had a cultural obligation to care for His mother, and He passed that obligation on to one of His closest friends. Mary was most likely one of the women in the upper room and was present when the church was established in Jerusalem (Acts 1:12–14). She probably continued to stay with John in Jerusalem until her death.

The beauty of John 19:26–27 is reflected in the care Jesus had for His mother, as well as the care John provided for her. Scripture clearly teaches the importance of caring for widows and the elderly, something Jesus personally applied during His final hours of His earthly ministry. James, the half-brother of Jesus, would later call such care for widows “pure religion.” “Religion that God our Father accepts as pure and faultless is this: to look after orphans and widows in their distress and to keep oneself from being polluted by the world” (James 1:27).