People are inconsistent. We say things we don't mean and try to change them later. We make rash promises and fail to keep them. We also make the mistake of projecting these traits onto God, imagining that his commands are flexible and his promises uncertain.
Unlike the flawed creation, the perfect Creator always means exactly what He says - a fact that the people of Noah's day learned too late. Decades after they were sure God had forgotten the world and Noah was crazy, the flood came and took them all away. God had not forgotten or changed his mind; only his patience was giving them every possible opportunity to change theirs (1 Pet. 3:20).
God's promises to Abraham are now several millenia old, yet we can see their fulfillment being worked out in the world today. His promises to us through Jesus Christ are no less reliable two thousand years after our Lord walked the earth. Take Him at his Word. You will find that every word is true, every time.
All Scripture references from KJV. Commentary ©2011 Hitchcock Family Ministry. Unaltered text may be reproduced freely without financial gain. Original commentary and Scripture song available at http://www.freescripturesongs.org/God-is-not-a-man.