People who say that ordination is no longer relevant in the modern world misunderstand its purpose. This method was taught by both Buddha and Jesus to protect us from delusions, to prevent us from harming ourselves or others. As a result of the karma of not harming others, we receive the immediate benefit of not being harmed by them, and experience great happiness and peace. Of course, there are long-term benefits as well: rebirth in the upper realms, liberation, and enlightenment.
Nevertheless, some people will still ask why today, when lay people can study and practice Dharma and attain enlightenment, is it necessary to live an ordained life?
It’s true that some lay people can practice well, but that doesn’t mean all lay people can practice well. Most lay people find it difficult. But just because Buddha and Jesus revealed the method of ordination doesn’t mean that everyone should become monks or nuns either. Everybody can’t become Sangha because everybody doesn’t have the karma to become Sangha. To do so you need a lot of merit and no inner obstacles. If there are no obstacles in your mind, there will be no outer obstacles to your ordination.
The main point here is that until you have developed a stable realization of the three principal aspects of the path in your mind, to practice Dharma properly you need to spend a lot of time away from the objects that induce your delusions to arise. This is especially true for beginners, but in fact applies to anybody not yet liberated from samsara. Hence, the need for monasteries and nunneries, caves and hermitages, and the discipline that goes along with living in such ascetic environments. And by living in places like those, you can easily see the importance of morality.
from Advice for Monks and Nuns by Lama Yeshe and Lama Zopa Rinpoche