A Bodhisattva resolves:
I take upon myself the burden of all suffering. I am resolved to do so, I will endure it. I do not turn or run away, do not tremble, am not terrified, nor afraid, do not turn back or despond.
And why? At all costs I must bear the burdens of all beings. In that I do not follow my own inclinations. I have made the vow to save all beings. All beings I must set free. The whole world of living beings I must rescue, from the terrors of birth, of old age, of sickness, of death and rebirth, of all kinds of moral offence, of all states of woe, of the whole cycle of birth-and-death, of the jungle of false views, of the loss of wholesome dharmas, of the concomitants of ignorance, from all these terrors I must rescue all beings. . . . I walk so that the kingdom of unsurpassed cognition is built up for all beings. My endeavours do not merely aim at my own deliverance. For with the help of the boat of the thought of all-knowledge, I must rescue all these beings from the stream of Samsara, which is so difficult to cross, I must pull them back from the great precipice, I must free them from all calamities, I must ferry them across the stream of Samsara. I myself must grapple with the whole mass of suffering of all beings. To the limit of my endurance I will experience in all the states of woe, found in any world system, all the abodes of suffering. And I must not cheat all beings out of my store of merit, I am resolved to abide in each single state of woe for numberless aeons; and so I will help all beings to freedom, in all the states of woe that may be found in any world system whatsoever.
And why? Because it is surely better that I alone should be in pain than that all these beings should fall into the states of woe. There I must give myself away as a pawn through which the whole world is redeemed from the terrors of the hells, of animal birth, of the world of Yama, and with this my own body I must experience, for the sake of all beings, the whole mass of all painful feelings. And on behalf of all beings I give surety for all beings, and in doing so I speak truthfully, am trustworthy, and do not go back on my word. I must not abandon all beings.
And why? There has arisen in me the will to win all-knowledge, with all beings for its object, that is to say, for the purpose of setting free the entire world of beings. And I have not set out for the supreme enlightenment from a desire for delights, not because I hope to experience the delights of the five-sense qualities, or because I wish to indulge in the pleasures of the senses. And I do not pursue the course of a Bodhisattva in order to achieve the array of delights that can be found in the various worlds of sense-desire.
And why? Truly no delights are all these delights of the world. All this indulging in the pleasures of the senses belongs to the sphere of Mara.
Sikshasamuccaya, 280-81 (Vajradhvaja Sutra)

To help others in vast and extensive ways we need to have attained one of the levels of a Bodhisattva, that is, to have experienced the direct non-conceptual reality of voidness and to have achieved the power of extra-sensory perception.

Question: When a practitioner of the Great Vehicle vows not to enter into nirvana until all beings are liberated, how is it possible to fulfill this vow?
Answer: Three modes of generating an altruistic intention to become enlightened are described--like a king, like a boatman, and like a shepherd. In the first, that like a king, one first seeks to attain a high state after which help can be given to others. In the second, like a boatman, one seeks to cross the river of suffering together with others. In the third, like a shepherd, one seeks to relieve the flock of suffering beings from pain first, oneself following afterward. These are indications of the style of the altruistic motivation for becoming enlightened; in actual fact, there is no way that a Bodhisattva either would want to or could delay achieving full enlightenment. As much as the motivation to help others increases, so much closer does one approach Buddhahood.
His Holiness the Dalai Lama, The Dalai Lama at Harvard by of Tibet