The phrase "Christ's method alone will make disciples" is actually a paraphrase of a well-known statement by Ellen G. White. The closest and most direct source is:
"Christ's method alone will give true success in reaching the people. The Saviour mingled with men as one who desired their good. He showed His sympathy for them, ministered to their needs, and won their confidence. Then He bade them, 'Follow Me.'"
— Ministry of Healing,
page 143.3 (
MH 143.3)
This same statement also appears in Gospel Workers,
page 363.2 (
GW 363.2).
While the exact phrase "will make disciples" is not used, the context and meaning are the same: Christ's method is the only effective way to reach people and make true disciples.
References:
- White, E. G. (1905). The Ministry of Healing, p. 143.3.
- White, E. G. (1915). Gospel Workers, p. 363.2.