Thus, if maternity and blood relation rights are obligatory upon a Muslim, in a way that exemplifies the beautiful manners of Islam and Muslims, it is also obligatory upon a Muslim to pay the due rights that work towards showing Muslims as people of beautiful character. The Prophet (peace and blessings be upon him) advised Abu Dharr (may Allah be pleased with him) saying: “Be aware of Allah wherever you are, and follow up a sin that you have committed with a good deed, so that sin may be erased, and treat people with beautiful manners.” (Reported by Ahmad, At-Tirmidhi, Ad-Darmi, and Al-Hakim) As is evident, the emphasis is upon “…and treat people with beautiful manners” not “…treat Muslims”.
The Prophet (peace and blessings be upon him) also strongly advised us to deal with non-Muslims in a mild and gentle manner, not using stern and terrorizing methods. It was reported that when a group of Jews approached the Prophet (peace and blessings be upon him) and greeted him with twisted pronunciation, and thus uttered “Assam`alaykum, O Muhammad!” (meaning “death and destruction come upon you”) instead of “as-salamu `alaykum”, `A'ishah (may Allah be pleased with her) heard them and responded by saying, ‘assamu `alaykum also and the curse and wrath of Allah!” The Prophet (peace and blessings be upon him) rebuked `A'ishah for what she had said. She told him, “Did you not hear what they said?” He said, “I did, and I responded by saying, ‘And upon you,’” (i.e., that death will come upon you as it will come upon me.) He went on to say, “O `A'ishah! Allah loves gentleness in all matters.” (Reported by Al-Bukhari and Muslim)
Indeed the permissibility of congratulating non-Muslims on their festive days becomes more of an obligation if they offer their greetings on Islamic festive occasions, as we are commanded to return good treatment with similar treatment, and to return the greeting with a better one or at least with the same greeting. Allah Almighty says: “When you are greeted with a greeting, greet in return with what is better than it, or at least return it equally…” (An-Nisa' 4: 86)
A Muslim must never be less charitable or pleasant or indeed of lesser manners than any other, as the Prophet (peace and blessings be upon him) stated in the hadith: “The most perfect believers in terms of their iman are those who possess the most beautiful manners.” (Reported by Ahmad, At-Tirmidhi, Ad-Darmi, and Abu Dawud), and he (peace and blessings be upon him) also stated: “Verily I have been but sent to perfect the most noble of manners.” (Reported by Ahmad, Al-Bukhari in Al-Adab Al-Mufrad and Al-Bazzar in Kashful Astar)