There is a good example to illustrate why Baba Ji has called SatNaam the diamond. In India a farmer may have ten acres of land which he ploughs, nurtures and grows his crop in. At harvest time the wheat he cuts may fill up many sacks, but still only take up a small area on his forecourt. When he sells those sacks of wheat he gets a large handful of notes. On the way home he buys a diamond the size of a pea. You can think of the whole of Guru Granth Sahib Ji as the ten acres of land, which you work hard to read and understand. Then you realise that the complete message of Guru Granth Sahib ji is contained in JapJi, the very first divine writing. After some time you find that just by doing Mool Manter you feel the divine essence of God that is described in 40 verses of JapJi.
Then when you receive the GurParsaad of SatNaam as described in Mool Mantr, you feel the whole essence of Guru Granth Sahib Ji in just one word, the Naam – “SAT – TRUTH. And that is the diamond that Baba ji realised through his inner pilgrimage that took him through every shabad of Guru Granth Sahib Ji and beyond.
So for the farmer, that diamond he purchased is extremely valuable as it represtents a whole year’s labouring in the fields. But, if the farmer gives the diamond to a pig, the pig will just trample it into the ground while it sticks its snout looking for food in the filth. But if the famer takes the diamond to a jeweller, the jeweller will be ready to bow to such beauty.
Baba Ji gives this diamond, the GurParsaad of SatNaam, to anyone who asks for it, as opposed to other Gurus who will want to assess wether you are a pig or a jeweller before giving you the spiritual earnings. But, Baba ji said for him he only sees God in whoever comes for the Naam so God in Baba Ji gives the diamond of SatNaam to God in the seeker and what they do with it is upto them, but Baba ji was in service and Baba ji did his job for the glory of SatNaam.