I let my beard grow and faced some criticism as a result. Some people said to me that faith is in the heart and not in the beard. I replied that this is true, but we must follow the Quran and the Sunnah which commands us to let our beards grow. Was my reply correct? What do you advise me to say in reply?

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

We ask Allaah The Almighty to guide us and you to what pleases Him, and to grant us firmness on the right path.

Your response was correct because it is obligatory upon for a Muslim to obey the commands of Allaah The Almighty and His Messenger, sallallaahu ‘alayhi wa sallam, among which is to let the grow the beard grow.  

However, your reply imperfect because you confirmed the claim that faith is in the heart, not in the beard. This statement is repeated by those people who  to escape the commands of Allaah The Almighty and the obligations of the Sharee'ah, without losing damaging their perception of themselves as faithful,  under the pretext counting on the fact that only Allaah The Almighty Knows what is inside the hearts.

This statement can be refuted in several ways:

- The creed of Ahlus-Sunnah (the Sunni mainstream) states that faith involves belief in the heart, profession with the tongue and deeds performed by parts of the body. Faith would not be attained unless all three are realized. This is indicated by the Quran, the Sunnah and the Imaams of the righteous predecessors. Thus, deeds are an indispensable part of faith. For extensive details on this issue you may refer to the books of creed compiled by the Imaams of Ahul-Sunnah.

- Also, Allaah The Almighty did not leave the door open for whoever wants to escape investigating the correctness or falsehood of this claim, rather deeds were made a verifying sign and an indication of what is in the heart.  Allaah The Almighty Says (what means): {Say, [O Muhammad], "If you should love Allaah, then follow me, [so] Allaah will love you.}[Quran 3:31]

Any person may claim that they love Allaah The Almighty as the basis of faith, like Jews and the Christians, as stated in the Saying of Allaah The Almighty (which means): {But the Jews and the Christians say, "We are the children of Allaah and His beloved.”}[Quran 5:18]  However Allaah The Almighty invalidated such unfounded claims by assigning a great sign for anyone who wishes to indicate his love for Him: following His Prophet, sallallaahu ‘alayhi wa sallam.

- We can also say to such people, how can you claim that faith is firmly established in your hearts and at the same time fail to obey the commands of Allaah whom you have faith in, fail to avoid His prohibitions and fail to follow the commands of the Messenger, sallallaahu ‘alayhi wa sallam, whom He sent as a person to warn and bear glad tidings?

And Allaah Knows best.