Praise be to Allah.
Shaping the eyebrows by trimming, shaving or plucking their edges in order to appear beautiful, as is done by some women nowadays, is haraam because it involves changing the creation of Allah and following the Shaytaan in his tempting of mankind to change the creation of Allah. Allah says (interpretation of the meaning):
“Verily! Allah forgives not (the sin of) setting up partners in worship with Him, but He forgives whom He pleases sins other than that, and whoever sets up partners in worship with Allah, has indeed strayed far away.
They (all those who worship others than Allah) invoke nothing but female deities besides Him, and they invoke nothing but Shaytaan, a persistent rebel!
Allah cursed him. And he [Shaytaan] said: ‘I will take an appointed portion of Your slaves;
Verily, I will mislead them, and surely, I will arouse in them false desires; and certainly, I will order them to slit the ears of cattle, and indeed I will order them to change the nature created by Allah.’ And whoever takes Shaytaan as a wali (protector or helper) instead of Allah, has surely suffered a manifest loss.” [Al-Nisa’ 4:116-119]
In al-Saheeh, it was reported that Ibn Mas’ood (may Allah be pleased with him) said: “Allah has cursed the women who do tattoos and those who have this done, the women who pluck eyebrows and those who have this done, and the women who file their teeth and change the creation of Allah.” Then he said: “Should I not curse those whom the Messenger of Allah (peace and blessings of Allah be upon him) cursed, when it says in the Qur’aan (interpretation of the meaning): ‘… And whatsoever the Messenger gives you, take it, and whatever he forbids you, abstain (from it)…’ [Al-Hashr 59:7]”