A:
There is nothing wrong in invoking Allah after Taslim specifically after finishing Adhkar (invocations) of Salah; because it is authentically reported in some Hadiths that it is permissible to do so. The hands should not be raised while invoking Allah after the Faridah (obligatory prayer), but there is nothing wrong with doing this after the Nafilah. Undoubtedly, Du‘a’ (supplication) before Taslim is better than making it after it, but it is not permissible
to raise one's hands while invoking Allah before Taslim; because it is considered a Bid‘ah (innovation in religion). The person who does so deserves bitter reproach because the Prophet (peace be upon him) said:
“Anyone who does an action which is not in accordance with this matter of ours (Islam) will have it rejected.”
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.