In the verses of the Quran, say "Insya Allah" ( If Allah wills)

" May Allah Bless you"
"If Allah wills"
" May Allah forgives you"


سُوۡرَةُ الکهف

وَلَا تَقُولَنَّ لِشَاْىۡءٍ إِنِّى فَاعِلٌ۬ ذَٲلِكَ غَدًا (٢٣) إِلَّآ أَن يَشَآءَ ٱللَّهُ‌ۚ وَٱذۡكُر رَّبَّكَ إِذَا نَسِيتَ وَقُلۡ عَسَىٰٓ أَن يَهۡدِيَنِ رَبِّى لِأَقۡرَبَ مِنۡ هَـٰذَا رَشَدً۬ا (٢٤)

Surah Al-Kahf

And never say of anything, "I shall do such and such thing tomorrow." (23) Except (with the saying), "If Allâh will!" And remember your Lord when you forget and say: "It may be that my Lord guides me unto a nearer way of truth than this." (24)