Not a command, but a helpful tool
You won't find a command saying every Christian should keep a prayer journal. Prayer is not made more acceptable to God by using a notebook, an app, or a particular routine. Jesus warns against prayer that is performed to impress people, and he points his followers towards sincere, God-focused prayer instead (Matthew 6:5-8).
So a journal is optional. You may pray while walking, driving, lying awake, speaking aloud, or sitting quietly. Yet writing can slow us down. It can help us name what is weighing on us, notice answers we might otherwise forget, and return to prayers that still need patience.
But thou, when thou prayest, enter into thy closet, and when thou hast shut thy door, pray to thy Father which is in secret; and thy Father which seeth in secret shall reward thee openly.
The Bible contains written prayers
Much of the book of Psalms is written prayer. David brings fear, grief, guilt, joy, anger, and trust before God with remarkable honesty. In Psalm 142, written when David was in a cave, he describes pouring out his complaint and showing God his trouble (Psalm 142:1-2). That is close to what many people do in a prayer journal.
Habakkuk also records a hard conversation with God. He asks why violence and injustice seem to continue, then waits attentively for God’s answer (Habakkuk 1:2-4; Habakkuk 2:1). Written prayer does not need to sound polished. It can make room for real questions and for waiting.
I poured out my complaint before him; I shewed before him my trouble.
Writing can help us remember
God repeatedly told Israel to remember his works. After Israel crossed the Jordan, Joshua set up stones as a visible reminder for future generations of what God had done for them (Joshua 4:6-7). A prayer journal can serve a similar purpose, not as a superstition, but as a personal record of God’s care.
You might write a concern, a person’s name, a verse that is shaping your prayer, or a later note about how the situation changed. Sometimes the answer will be clear. Sometimes it will be different from what you hoped. Looking back can still help you recognise God’s presence and grow in trust.
Keep it honest and simple
A prayer journal is useful only if it draws you towards God, not if it becomes another burden. Paul encourages believers to bring every need to God with prayer, supplication, and thanksgiving (Philippians 4:6). A few unguarded lines can be enough.
Try writing a short prayer from your own life: what you are thankful for, what hurts, what you need, and whom you want God to help. You can also write a psalm in your own words and answer it with prayer. If journalling doesn't suit you, you are not missing a requirement. God hears the heart that comes to him.
Be careful for nothing; but in every thing by prayer and supplication with thanksgiving let your requests be made known unto God.