For I said in my haste; rather, and I indeed had said in my haste (comp. Psalms 116:11). David's faith was not so firmly fixed but that he was liable, from time to time, to a sudden access of fear (see 1 Samuel 27:1; 2 Samuel 15:14; Psalms 31:13).
He had said to God in his heart, on one such occasion, I am cut off from before thine eyes; i.e. he had despaired and given himself up for lost. It is somewhat forced to understand the words as meaning, "I am banished from the city where the ark is placed" ('Speaker's Commentary').
Nevertheless, thou heardest the voice of my supplications when I cried unto thee. God did not forsake his servant on account of this temporary failure of faith. No sooner did the psalmist rid himself of his extreme alarm, and turn once more to God in prayer, than he was heard, and his prayer answered.