I never understood what Sanatana Dharma meant. Conversation of Vasudeva with Sri Aurobindo helped me understand it and the reasons behind spread of yoga, gita, vedas all over the world.

Words of Sri Aurobindo on Sanatan Dharma:

He said to me, “When you were cast into jail, did not your heart fail and did you not cry out to me, where is Thy protection? Look now at the Magistrate, look now at the Prosecuting Counsel.” I looked and it was not the Magistrate whom I saw, it was Vasudeva, it was Narayana who was sitting there on the bench. I looked at the Prosecuting Counsel and it was not the Counsel for the prosecution that I saw; it was Srikrishna who sat there, it was my Lover and Friend who sat there and smiled. “Now do you fear?” He said, “I am in all men and I overrule their actions and their words. My protection is still with you and you shall not fear. This case which is brought against you, leave it in my hands. It is not for you. It was not for the trial that I brought you here but for something else. The case itself is only a means for my work and nothing more.”…

“I am guiding, therefore fear not. Turn to your own work for which I have brought you to jail and when you come out, remember never to fear, never to hesitate. Remember that it is I who am doing this, not you nor any other. Therefore whatever clouds may come, whatever dangers and sufferings, whatever difficulties, whatever impossibilities, there is nothing impossible, nothing difficult. I am in the nation and its uprising and I am Vasudeva, I am Narayana, and what I will, shall be, not what others will. What I choose to bring about, no human power can stay.”…

He said to me, “This is the young generation, the new and mighty nation that is arising at my command. They are greater than yourself. What have you to fear? If you stood aside or slept, the work would still be done. If you were cast aside tomorrow, here are the young men who will take up your work and do it more mightily than you have ever done. You have only got some strength from me to speak a word to this nation which will help to raise it.” This was the next thing He told me….

I felt there must be a mighty truth somewhere in this Yoga, a mighty truth in this religion based on the Vedanta. So when I turned to the Yoga and resolved to practise it and find out if my idea was right, I did it in this spirit and with this prayer to Him, “If Thou art, then Thou knowest my heart. Thou knowest that I do not ask for Mukti, I do not ask for anything which others ask for. I ask only for strength to uplift this nation, I ask only to be allowed to live and work for this people whom I love and to whom I pray that I may devote my life.”…

“Something has been shown to you in this year of seclusion, something about which you had your doubts and it is the truth of the Hindu religion. It is this religion that I am raising up before the world, it is this that I have perfected and developed through the rishis, saints and avatars, and now it is going forth to do my work among the nations. I am raising up this nation to send forth my word. This is the Sanatana Dharma, this is the eternal religion which you did not really know before, but which I have now revealed to you. The agnostic and the sceptic in you have been answered, for I have given you proofs within and without you, physical and subjective, which have satisfied you. When you go forth, speak to your nation always this word that it is for the Sanatana Dharma that they arise, it is for the world and not for themselves that they arise. I am giving them freedom for the service of the world. When therefore it is said that India shall rise, it is the Sanatana Dharma that shall rise. When it is said that India shall be great, it is the Sanatana Dharma that shall be great. When it is said that India shall expand and extend herself, it is the Sanatana Dharma that shall expand and extend itself over the world. It is for the dharma and by the dharma that India exists. To magnify the religion means to magnify the country. I have shown you that I am everywhere and in all men and in all things, that I am in this movement and I am not only working in those who are striving for the country but I am working also in those who oppose them and stand in their path. I am working in everybody and whatever men may think or do they can do nothing but help on my purpose. They also are doing my work; they are not my enemies but my instruments. In all your actions you are moving forward without knowing which way you move. You mean to do one thing and you do another. You aim at a result and your efforts subserve one that is different or contrary. It is Shakti that has gone forth and entered into the people. Since long ago I have been preparing this uprising and now the time has come and it is I who will lead it to its fulfilment.”

Hope its useful for younger generation

Jai Shri Hari!!!