Insha'Allah (ان شاء الله ) is an Arabic phrase evoked by Muslims to indicate hope for an aforementioned event to occur in the future. The closest equivalent English phrase is "God willing", though the Arabic term bears a stronger religious connotation.
This word is often used to indicate a desire to do something that may not actually occur. This also provides wiggle room for someone who may feel obligated to agree to something, but prefer not to do it.
Usage of Insha'Allah derives from Islamic scripture, Sura Al Kahf (18):23 : "And never say of anything, 'I shall do such and such thing tomorrow. Except (with the saying): 'If Allah wills!' And remember your lord when you forget..."
Muslim scholar Ibn Abbas stated that it is in fact obligatory for a Muslim to say Insha'Allah when referring to something he or she intends to do in the future. If carelessless leads to the omission of the phrase, it may be said at a later time upon the realization of the omission.
The Spanish word ojalá (I hope, I wish) is derived from law šá lláh, a phrase meaning "God willing." It is one of many words borrowed from Arabic due to the Muslim possession of part of Spain from the eighth to fifteenth centuries.