This term is found in the Ofudesaki:
Have your strongest come against Me. God has twice the strength.
The verse can be interpreted as saying that, however strong a person pitted against God may be, God is always twice as strong. The Scripture goes on to say:
As God in Truth is going out to the fore, know that every arrangement will be made.
Based on this verse, we might also interpret the Ofudesaki as saying that God will double the strength of those who endeavor to spread the teachings.
A similar theme appears in Anecdotes of Oya-sama, in which Oyasama invites followers to pit their strength against Hers, so that they might be convinced that She was indeed the Shrine of Tsukihi. According to Anecdote no. 152, Oyasama told Unosuke Tosa (who later founded what was to become Muya Grand Church) in about 1884 when he returned to Jiba with many followers: "Tosa, you are here from a distant place, but if you do not realize the true strength of God, you will feel uneasy in bringing back many followers. Why don't you try God's strength today?" Oyasama told an attendant to bring a hand towel and, holding one end of it by pinching it between Her thumb and index finger, She asked Tosa to hold the other end and pull it toward himself with all his might. Always a strong-armed man, Tosa was proud of the strength that he had gained as a sailor, yet he could not draw the towel closer to himself. Next, Oyasama stretched Her right hand toward him and said: "Try once more. Now hold Me by the wrist this time." Tosa then respectfully did as he was told. The more strongly he grasped it, the more painful his hand became. So he bowed deeply before Oyasama, saying, "I am overwhelmed." Then She said to him with a pleasant smile: "This is God's strength. Twice as strong as yours."
Another story in Anecdotes of Oyasama (no. 174) tells about Hidenobu Nakano, who had been in charge of horses for the Koizumi feudal clan in Ya-mato Province and was also proficient in jujitsu (the martial art from which judo developed) and kendo (Japanese swordsmanship). He returned to Jiba one day and was granted an audience with Oyasama, during which She took hold of both his wrists, saying: "Nakano, you are known as a strong man in the country. Now try and remove your hands." With a shout, Nakano tried with all his might to pull both hands free. Though he tried again and again, shouting each time, She remained steady with perfect composure. Not only that, the more he exerted his strength, the more strongly his own wrists were gripped. Finally, they started to feel as if they were being ripped apart. Nakano could no longer bear the pain and said: "I am overwhelmed. Please release my hands." Then She said: "If you let go your strength, God will also let go God's strength. If you exert strength, God will also exert strength. This applies not only now but always."
(This article was first published in the March 2010 issue of TENRIKYO.)