Does a Muslim leave the fold of Islam if he intentionally neglects a fard (obligatory) prayer until its time has expired, and what is the expiation for that, knowing that he completed his ablution, then doubted whether he had forgotten to wipe his ears, so he wiped them again and washed his feet, then prayed Maghrib, and after that, he repeated the ablution and prayer with the intention of qada (making up the missed prayer) believing that the Maghrib prayer must be performed within its original time?

Wiping the ears in ablution is a Sunnah (recommended act) according to the majority of scholars. Therefore, whoever omits it is not required to repeat the ablution nor what comes after it. As for making up for it, the jurists have differed in their opinions. The Malikis, Shafi'is, and Hanbalis do not consider it permissible to make up for it if its designated time has passed. The Malikis hold that a Sunnah should be redone if it was performed incorrectly due to forgetfulness or intentionally. However, if it was completely omitted (like sniffing water into the nose or wiping the ears), one should perform it as a Sunnah without repeating what came after it. Similarly, the Shafi'is do not consider performing Sunnah acts valid after their designated time has passed. Your repetition of the prayer due to omitting the wiping of the ears is not justified, and your initial prayer was valid, because wiping the ears is a Sunnah which does not invalidate the prayer by its omission. Delaying prayer beyond its prescribed time without a legitimate excuse is a sin, but the one who commits it is not considered a disbeliever unless he denies the obligation of prayer.