I heard from several people that making du’a after prayer(s) is not allowed except for a few cases. Only Allah knows where this opinion comes from, I don’t know, I have never heard or read this. I remember to have read somewhere though, which book exactly I don’t know, that after prayer(s) it is (one of the) recommended time(s) to make du’a (I mean after prayer, next to sujud which is one of the most recommended times). After reading several texts on this subject I decided to collect af few verses of the Qur’an and some ahadith on this topic which make one hopefully – insha’Allah – conclude otherwise and Allah knows best. To Him we turn with our du’a and He is the One who accepts our du’a in the end or not.
– Call me, I shall answer you. [Q. 40:60]
– Supplication is the essence (or the pith) of worship. (Bukhari)
– Glad tidings are for him who finds abundant invocations for forgiveness recorded in his book of deeds. (Ibn Majah)
– Nothing is more honored in the sight of Allah than supplication. (Tirmidhi, Ibn Majah)
– Whoever does not ask Allah, Allah becomes angry with him. (Tirmidhi, Ahmad)
These are just a couple of ahadith on the topic. I have taken them from Provisions for the Seekers (Zad at-Talibin) only, personally I always make du’a after prayers. A topical study on du’a is in preparation insha’Allah.
Looking into Bulugh al-Mar’am by imam Ibn Hajar al-Asqalani rahimuhullah, the chapter on Remembering Allah and Supplication, I came across the following ahadith (which support the above):
– Verily supplication is worship. (Related by the four imams and at-Tirmidhi graded it sahih).
– Nothing is more honourable before Allah than supplication. (at-Tirmidhi. Graded as sahih by Ibn Hibban and al-Hakim)
– Your Rabb (Lord of the Universe) is Modest and Generous, and would never turn the hands of a slave without gain when he raises them to Him. (Related by the four imams, graded sahih by al-Hakim)
There is also a hadith qudsi in this respect: “…if he calls upon Me, I answer him, and if he asks of Me, I will give him…”
Allah’s door is always open, He is always there and He is All-hearing, and we can make du’a any time we like, this is what I understand – with my limited knowledge – from the above.