Bhikkhus, I am freed from all snares, both celestial and human. You too, bhikkhus, are freed from all snares, both celestial and human. Wander forth, O bhikkhus, for the welfare of the multitude, for the happiness of the multitude, out of compassion for the world, for the good, welfare, and happiness of devas and humans. Let not two go the same way. Teach, O bhikkhus, the Dhamma that is good in the beginning, good in the middle, good in the end, with the right meaning and phrasing. Reveal the perfectly complete and purified holy life. There are beings with little dust in their eyes who are falling away because they do not hear the Dhamma.  There will be those who will understand the Dhamma. I too, bhikkhus, will go to Senānigama in Uruvelā in order to teach the Dhamma.”
It is right after sixty disciples achieved Arahantship by the buddha’s teaching and guidance. The Buddha encourages them to go and travel around the world to teach the Dhamma for people have not heard about the dhamma yet.
The reason that the Buddha encourages them to spread his teaching in the world is just for the happiness and welfare of the people. It is not for money, fame, popularity, or likes on facebook or instagram, or any other worldly gain.
The very motivation that his disciples including the Buddha himself had to travel around the vast Indian continent was because of compassion, the compassion that one cannot tolerate other people’s suffering.
According to Buddhism, in the world that is governed by invisble law that is co dependent arising, no one cannot be happy right next to others who are not happy. Likewise, we cannot tolerate the misery of our family, freinds, acquaintances, even the people who live far away from where we live now
What the buddha and his enlightened disciples did for the people was like “Making Buddhism” to appear in the world as a source of happiness.
Interestingly, the passage also indicates that for the propagation of the dhamma, the Buddha only encourages the people who is enlightened and attained arahantship.
And then questions can follow like “is someone who is not enlightened can teach the dhamma? or ” why did the buddha only urge no one else, but arahants to travel around the world and to teach his teaching?
However, we, not yet enligthened, can share the Dhamma based our experience and learning of it to make the world better.