Quotes from The Lotus Sutra, Vol. 1
"With the power of skillful means,
I have revealed the Dharma of three vehicles;
Yet all the World-Honored Ones
Teach the One Vehicle way.
Now everyone in this great assembly
Should rid themselves of doubt.
The Buddhas do not differ in their claim
That there is only One Vehicle, not two.
. . . . . . .
All these World-Honored Ones
Have taught the Dharma of One Vehicle,
Transforming countless living beings,
Enabling them to enter the Buddha way.
Moreover, all the great saints
Knowing the deepest desires of all the gods,
Humans, and other beings of all the worlds,
Have still other skillful means to further clarify the ultimate truth.
Reference: Gene Reeves, (2008) The Lotus Sutra: A Contemporary Translation of a Buddhist Classics, p.91
Excerpts From A Discourse on The Lotus Sutra
Venerable Xiao Pingshi
All buddhas achieved Buddhahood by practicing the bodhisattva way. There can never be a buddha who attained Buddhahood by practicing the ways of the solitary realizers or sound hearers. As all buddhas have practiced the bodhisattva way, whose cultivation leads to the attainment of the Buddha Bodhi, what they have realized is most certainly the teaching of the One Vehicle: the single Buddha Vehicle, which is the path toward the attainment of the Buddha Bodhi. Thus, when they manifest in the human world, they will certainly expound this One Vehicle. However, because it is difficult for sentient beings living in the impure world of five turbidities (the Saha world) to accept the teaching of the One Vehicle, all buddhas employ their skillful means to demonstrate and reveal the three separate vehicles for us. Yet, in the end, they will always expound the one and only Buddha Vehicle and will not depart from the human world after teaching only the two vehicles (the solitary realizers or sound hearers).
A Discourse on the Lotus Sutra, Vol. 3, pp.129-130