Sheikh `Abd Allah Nâsir al-Sulamî, professor at the Higher Juridical Institute
The preferable opinion in this regard is to say that salutations among Muslims for `Id and Ramadan do not come under the category of worship but under that of general customs. this was the opinion of late Sheikh `Abd al-Rahmân b. Sa`dî.
Sheikh Ibn Bâz went further and said that it is a preferable practice and cites a hadîth that the Prophet (peace be upon him) said: “Ramadan is approaching you. It is a blessed (mubârak) month”. It was narrated in this context by al-Tirmidhî and Ahmad from the hadîth of Abû Hurayrah. The hadîth itself is actually in the form of a salutation. This hadîth, however, is weak.
Nevertheless, we could say that offering salutations to others is permissible even if there is no authentic hadîth from the Prophet (peace be upon him), because the one who does this is merely offering a short supplication for his fellow Muslim.
It is authenticated that the Prophet (peace be upon him) congratulated Ka`b b. Mâlik for Allah accepting his repentance. This would prove that it is alright to congratulate someone who gets something good. The Prophet (peace be upon him) congratulated Ka`b b. Mâlik by saying “Be happy with Allah’s acceptance of your repentance.”
The arrival of the month of Ramadan is a cause of great happiness for Muslims and an occasion for salutations to be exchanged.
And Allah knows best.
Source: Islam Today