Praise be to Allah the Lord of the Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
There is a consensus amongst the scholars of Islamic jurisprudence that the Quran is expressly established, but in terms of indication, it could be expressly or ambiguously indicative. As for the Prophetic Sunnah, some of it is expressly established and expressly indicative while some is ambiguously established and ambiguously indicative.
According to the Principles of Islamic Jurisprudence (usul al-fiqh), the Sunnah explains and clarifies the Quran. Allah the Almighty Says {What means}: "(We sent them) with Clear Signs and Books of dark prophecies; and We have sent down unto thee (also) the Message; that thou mayest explain clearly to men what is sent for them, and that they may give thought." {An-Nahil, 44}. Allah also Says {What means}: "And We sent down the Book to thee for the express purpose, that thou shouldst make clear to them those things in which they differ, and that it should be a guide and a mercy to those who believe." {An-Nahil}. The Prophet (Peace be upon him) said: Beware! I have been given the Qur'an and something like it, yet the time is coming when a man replete on his couch will say: Keep to the Qur'an; what you find in it to be permissible treat as permissible, and what you find in it to be prohibited treat as prohibited." {At-Tirmithi, 2664}.
The sound scientific method rests on bringing together verses and Hadiths in light of the principles of Islamic jurisprudence and derives legal rulings from them as an integrated whole since they come from the same source. Moreover, all the methods that aim to exclude the Prophetic Sunnah, under any pretext, are destructive rather than constructive and they contradict the intellect as well as the texts of Sharia.
As regards the verses referred to in the above question: chapter Al-Baqarah, verse (217); chapter Al-Ma`idah, verse (54), and chapter Al-Nisa`, verse (137/138), none of them negates the prescribed punishment for apostasy nor mentions a worldly punishment for it. Rather, they state the punishment awaiting the apostate in the Hereafter and this doesn`t contradict in some respect with what is established in the Sunnah regarding apostasy reflected in the narration where the where the Prophetr {Peace be upon him} said: “He who changes his religion (i.e. apostates) kill him.” [Related by Al-Bukhari].
We recommend that the asker responders upon the above verses and rest assured that there is no disagreement between the Quran and the authentic Sunnah. And Allah The Almighty Knows Best .