When 🧝Luthien wore the 💎silmaril in Ossiriand...

[Feanor]

the sons of Feanor knew she bore it but never made any move towards trying to obtain it or even ask for it. Any idea why?

 

[aragil]

It certainly goes against the wording of their oath, where they (Feanor and sons) expressly hold themselves to pursue any in Arda that hold a Silmaril- man, elf, maia (presumably Luthien falls somewhere between these last two) or vala. However, at this time Maedhros was still able to restrain his brothers, and he was against attacking fellow Elves to retrieve the Silmaril, in spite of what he said in the oath. When the brothers finally do attack Doriath, he is still against the action, but it is implied that he is over-ruled by Celegorm, Caranthir, and Curufin. These last three are ever-ready to fulfill the oath, but do not seem to be nearly as brave or valiant as Maedhros. Perhaps Celegorm and Curufin in particular remembered what happened to them the last time they attacked Luthien, and so considered the enterprise hopeless. However, it appears it was equally hopeless for them to attack Dior, as I believe he slew at least one (if not both) of the duo.

Incidentally, I have a real problem with the later attack on the havens. Maedhros is said to have foresworn the oath (and was especially upset at the apparent death of Elured and Elurin following the oath's work in Doriath), and at first he declined to attack the havens. Yet he was tormented by the oath, and eventually led the four remaining brothers in the attack. The Oath itself was sworn to Illuvatar, and Mandos and Manwe were named as witnesses. Of these three, it is unclear to me which one would not have released Maedhros from the oath when he foreswore it. In the justice system in my mind (probably different than that of Manwe or Eru), the guilt of the third kinslaying fell not to Maedhros and the sons of Feanor (who had foresworn their oath), but to whichever of the three named who did not release the brothers from their oath. I guess such cold adherence to an evil oath in the face of repentance does not sit well with me.

 

[Tyaronumen]

Hmmm -- I suppose that I have doubts as to whether one of the Valar could have released Maedhros from his oath, seeing as how it an oath to Iluvatar, and not to the Valar.

Iluvatar could have, I suppose, mitigated the oath of Maedhros -- but for what purpose?

 

[Tyaronumen]

Hmmm -- I suppose that I have doubts as to whether one of the Valar could have released Maedhros from his oath, seeing as how it an oath to Iluvatar, and not to the Valar.

Iluvatar could have, I suppose, mitigated the oath of Maedhros -- but for what purpose?

 

[Maedhros]

And Maedhros answered: 'But how shall our voices reach to Ilúvatar beyond the Circles of the World? And by Ilúvatar we swore in our madness, and called the Everlasting Darkness upon us, if we kept not our word. Who shall release us?'

Maedhros gave his word, and he keeped it to the very end.

Then Fëanor swore a terrible oath. His seven sons leapt straightway to his side and took the selfsame vow together, and red as blood shone their drawn swords in the glare of the torches. They swore an oath which none shall break, and none should take, by the name even of Ilúvatar, calling the Everlasting Dark upon them if they kept it not; and Manwë they named in witness, and Varda, and the hallowed mountain of Taniquetil, vowing to pursue with vengeance and hatred to the ends of the World Vala, Demon, Elf or Man as yet unborn, or any creature, great or small, good or evil, that time should bring forth unto the end of days, whoso should hold or take or keep a Silmaril from their possession.

Eru was the only one who could undo the oath.

 

[Ravenna]

Whether it be because of her deeds in aiding Beren to recover the Silmaril, or because of her prayers and choices before Mandos, or the simple fact that she and Beren had been sent back by Manwe to live on for a period, it states in the book that when Luthien and Beren passed from the world and Dior wore the Nauglamir, 'the oath of the sons of Feanor was waked again from sleep. For while Luthien wore the Necklace of the Dwarves, no elf would dare assail her'.
Whatever the reason, all elves, even the sons of Feanor respected and honoured her so much that the oath 'slept' for a while, before forcing them once again to attempt to regain their father's jewel.