Sunnah
The narration about 50 salats is not authentic. When God issues a commandment, he does not negotiate with his creations, even if they are Prophets. Please refer to verse 11:76, Qur 11:76 “ O Abraham, turn away from this. The command of your Lord has been passed , and a retribution that will not be turned back is coming for them.” The narration about 50 prayers is nothing but an invented story. Zoroastrians pray five times a day. While in Judaism, the number of daily prayers is three. Some people argue that number of prayers in Judaism was originally five. But this is a speculation, and not grounded in proper evidence. The preponderance of evidence, both from Bible and Talmud suggests that the number of prayers in Judaism has been three, practiced to this day. Please see Psalms 55:18, Daniel 6:11. Please note that SunnatuAllah (God’s law, way of dealing) is immutable and does not change (33:62, 35:43, 17:77, 48:23). Whereas, salat is a commandment or an act of worship prescribed by God, and God’s commandments towards humans changed with time in past. For instance, with respect to the mandate of Jesus, please see verse 3:50: Qur 3:50 “And authenticating what is between my hands of the Torah, and to make lawful some of that which was made unlawful to you ; and I have come to you with a sign from your Lord, so be aware of God and obey me.” Also see verse 4:160 which tells that God changed certain laws for Jews because of their wickedness: Qur 4:160 Because of the wickedness from those who are Jews, We made forbidden to them the good things that were lawful to them, and for their deterring many from the path of God.