Is silent prayer biblical?

TL;DR:

Silent prayer is biblical because God hears our thoughts. Depending on the situation, praying silently can be more appropriate and just as powerful as praying aloud.

The Bible teaches that God accepts silent prayer. One Old Testament example is Hannah praying silently in 1 Samuel 1:12-13. God hears even our silent prayers because He is omniscient and knows our thoughts (Psalm 139:1-4; Jeremiah 17:10; Luke 16:15). We are called to pray constantly (1 Thessalonians 5:17; Ephesians 6:18), which implies that some of our prayers will be silent. Furthermore, during times in which we can neither verbalize nor mentally elaborate on what we are trying to say to God, we can know that the Holy Spirit is at work within us, interceding on our behalf to Father God (Romans 8:26). God hears our prayers—whether they are spoken silently or out loud.

from the old testament

God can hear our thoughts (Psalm 139:1-4). When we pray silently, He is still there. Silent prayer is still a prayer of confidence and faith.
In 1 Samuel 1:12-13, Hannah prayed silently, and her request was later granted.

from the new testament

Though Jesus does not specifically mention "silent prayer", He does talk about praying alone (Matthew 6:6). No matter where or how we are praying, God hears the prayers of His children.
First Thessalonians 5:17 tells us to “pray without ceasing.” Sometimes, it is more conducive to pray silently than aloud, and that’s okay.
What’s important is that we value prayer enough to engage in it at all times and that we pray in the Spirit (Ephesians 6:18), aloud or silently.
Romans 8:26 says that sometimes we do not know what to pray and the Holy Spirit intercedes for us. This implies silent prayer.

implications for today

There is power in the spoken word. We tend to be more confident in what we pray when we speak it. For others to agree with us in prayer, they must hear our prayer. But there is also power in silent prayer. We are instructed to pray constantly (1 Thessalonians 5:17), and obviously praying silently to God is at times more conducive to our situation. If you’re giving a presentation or praying for the person to whom we are presently speaking with, silent prayer is appropriate. Our omniscient Lord knows our thoughts, so He hears our prayers, even if they’re silent.

As Solomon wrote, there is “a time to keep silence, and a time to speak” (Ecclesiastes 3:7). Sometimes, praying silently fits the situation. More important than whether our words can be heard or not is that we are praying continually in the Spirit (Ephesians 6:18) and praying for everyone (1 Timothy 2:1).

understand

God is omniscient, so He hears even our silent prayers.
The Bible teaches us to “pray without ceasing” (1 Thessalonians 5:17), which implies silent prayer.
More important than if we pray aloud or silently is praying with sincerity, in the Spirit.

reflect

When do you find silent prayer most natural or effective?
What do you learn about your own heart and intentions when you practice silent prayer?
What differences, if any, do you notice about your silent prayers versus praying aloud?

engage

Why might some people not think of silent prayer as “real” prayer?
What does it mean and what does it look like practically to “pray without ceasing”?
How might the fact that God knows our thoughts impact the way we pray?