Notice that the verse says that angels are “heeding the voice of His word”. Now, who gives voice to God’s Word? We do! Each time we speak God’s Word, we give voice to His Word. And when angels hear His Word given voice, they respond!
The Bible says that at the end of Daniel’s three weeks of fasting and praying for an answer from God, the angel Gabriel appeared to Daniel and said to him, “I have come because of your words.” (Daniel 10:12)
So when angels hear you saying, “Thank You, Father, no evil shall befall me nor shall any plague come near my dwelling,” (Psalm 91:10) they will come to your aid because you are giving voice to God’s Word. Even if you cannot quote the verse perfectly, they can still come to your rescue.
However, if you know God’s Word by heart but refuse to proclaim it, the power of His Word cannot be released. The Bible does not say that angels heed His Word. No, it says that “His angels, who excel in strength, who do His word, heeding the voice of His word”. So , give voice to God’s Word and see His angels respond. His angels are activated for your benefit when you speak His Word!