Praise be to Allah.
With regard to the izar (lower garment or waist wrapper ) and rida (upper garment) for the man in ihram , the Sunnah is that they should be white and clean; it is not essential that they be new.
Ibn Qudamah said in al-Mughni (10/76):
“He should wear two clean garments, namely the izar and rida. The Messenger of Allah (blessings and peace of Allah be upon him) said: “Let one of you enter ihram in an izar and rida and sandals.”
It is mustahabb for the izar and rida to be clean, either new or washed, because we like for him to be clean in his body and also in his clothing. It is better for them to be white, because the Prophet (blessings and peace of Allah be upon him) said: “The best of your garments are those which are white; dress your living ones in them and shroud your dead ones in them.”
Shaykh Ibn ‘Uthaymin (may Allah have mercy on him) said:
“It is not essential for the izar and rida to be new, but it is mustahabb to enter ihram in two clean white garments; the cleaner the better, because Allah is Beautiful and loves beauty.” (Majmu’ al-Fatawa by Ibn ‘Uthaymin, 22/12)
And Allah knows best.