Regarding his supplication, Allah says:

رَبِّ اشْرَحْ لِي صَدْرِي ﴿٢٥﴾ وَيَسِّرْ لِي أَمْرِي ﴿٢٦﴾ وَاحْلُلْ عُقْدَةً مِّن لِّسَانِي ﴿٢٧﴾ يَفْقَهُوا قَوْلِي ﴿٢٨﴾

Rabbish-rah lee sadree. Wa yassir leee amree. Wahlul 'uqdatam-mil-lisaanee. Yafqahoo qawlee.

My Lord, expand for me my breast [with assurance] (25) And ease for me my task(26) And untie the knot from my tongue(27) That they may understand my speech.(28)

Reference: Surah Ta Ha 20: 25-28