A 'stretched out arm,' as in Exodus 6:6, signifies omnipotence or divine power, because 'an arm,' when stretched out in the heavens, represents power from the divine, but when not stretched out, but bended, it represents power in the general sense. This is why divine power is often shown in the Word as a stretched out arm or a strong hand.

(References: Arcana Coelestia 7205)

6982. 'I am not a man of words' means that he is lacking in speech. This is clear from the meaning of 'a man of words' as the fact that he is not an able speaker, and so is lacking in speech. What all this entails must be stated. The subject here in the highest sense is the Lord, for 'Moses' represents the Lord in respect of the law of God, thus in respect of God's truth. Truth that goes forth directly from the Divine cannot be heard by anyone, not even by any angel; if what is Divine is to be heard it must first be made human, and it is made human when it passes through the heavens. When it has passed through the heavens it is presented in a human form and becomes speech, speech which is uttered by spirits who, while they are in that state, are called the Holy Spirit. But the Holy Spirit is said to come forth from the Divine because what is holy with a spirit, namely the holy truth uttered by him at that time, comes forth from the Lord. From all this one may recognize that truth coming forth directly from the Divine cannot be presented to anyone as spoken word or speech except by means of the Holy Spirit. This is what is meant in the highest sense when Moses, who represents the Lord in respect of God's truth, says that he is 'not a man of words', and by the fact that Aaron his brother was to be attached to him; Aaron was to serve him in place of his mouth, and he was to serve Aaron in God's place.