And Imam al-Sadiq (a.s.) said:

"Dissimulation is obligatory upon every believer. Do you not see the saying of the Almighty: {And if you are patient and fear Allah, that indeed is of the matters of determination} (Al-Imran: 186)?"

And he said:

"The believer’s fortress is dissimulation, and his sword is fortification from the whispers of the soul."

Among the proofs for the intense obligation of protecting ourselves from the disbelievers by concealing the Inward (Al-Batin)—symbolized by the shortening of prayer (Qasr al-Salat)—and veiling ourselves by establishing the Outward (Al-Zahir)—symbolized by the prayer of fear and travel (Salat al-Khawf wa al-Safar)—is what the Almighty pointed to in Surah An-Nisa:

{And when you travel throughout the land, there is no blame upon you for shortening the prayer if you fear that those who disbelieve may disrupt [harm] you. Indeed, the disbelievers are ever to you a clear enemy. And when you are among them and lead them in prayer, let a group of them stand [in prayer] with you and let them carry their arms.