My heart was hot within me - My mind became more and more excited; my feelings more and more intense. The attempt to suppress my emotions only more and more enkindled them.
While I was musing the fire burned - literally, “in my meditation the fire burned.” That is, while I was dwelling on the subject; while I was agitating it in my mind; while I thought about it - the flame was enkindled, and my thoughts found utterance. He was unable longer to suppress his feelings, and he gave vent to them in words. Compare Jeremiah 20:9; Job 32:18-19.
Then spake I with my tongue - That is, in the words which are recorded in this psalm. He gave vent to his pent-up feelings in the language which follows. Even though there was a feeling of murmuring and complaining, he sought relief in stating his real difficulties before God, and in seeking from him direction and support.