But the New Testament supersedes the Old Testament...
In Christian Theology, the old testament is now a historical document, not the current operating manual for life.
We no longer have to paint blood on the doors over passover or toss the yeast, and all the rest of the requirements of making burnt offerings on altars et al are obsolete.
In Islam, if two statements conflict, the older has precedence... Think of what life would be like if the Ops Manuals could never be updated. changed, altered, varied or adjusted.
Which is part of why good Muslims loathe Bahaii, their religion is an offshoot of Islam as Islam is a perverted used camel salesmans offshoot of Christianity.
Mohammed used to be a Christian, before he started his own cult and marched off into the desert to convert the heathen, taking a large proportion of the Monophysite Christian heretics of the time with him. This left the dominant Dyophysite Christians that made up the Church of Rome/Catholic Church to dominate the theology until the Muslim hordes came out of Asia and took the holy land, sparking the Crusades.