diff --git a/xml/System.Linq.Expressions/Expression.xml b/xml/System.Linq.Expressions/Expression.xml
index afb05ada36c..317f0f883ac 100644
--- a/xml/System.Linq.Expressions/Expression.xml
+++ b/xml/System.Linq.Expressions/Expression.xml
@@ -2334,6 +2334,8 @@ If the implementing method is `null`:
 ## Remarks
  When the block expression is executed, it returns the value of the last expression in the block.
 
+If you pass a <xref:System.Collections.ObjectModel.ReadOnlyCollection%601> instance as the `expressions` argument, the returned <xref:System.Linq.Expressions.BlockExpression> might reuse that collection instead of copying it. Do not modify the collection's underlying storage after creating the block. If the source can be mutated, create a stable snapshot before passing it to this method.
+
  ]]></format>
         </remarks>
       </Docs>
@@ -2463,6 +2465,8 @@ If the implementing method is `null`:
 ## Remarks
  When the block expression is executed, it returns the value of the last expression in the block.
 
+If you pass a <xref:System.Collections.ObjectModel.ReadOnlyCollection%601> instance as the `expressions` argument, the returned <xref:System.Linq.Expressions.BlockExpression> might reuse that collection instead of copying it. Do not modify the collection's underlying storage after creating the block. If the source can be mutated, create a stable snapshot before passing it to this method.
+
 
 
 ## Examples
@@ -2696,7 +2700,14 @@ If the implementing method is `null`:
         <param name="expressions">The expressions in the block.</param>
         <summary>Creates a <see cref="T:System.Linq.Expressions.BlockExpression" /> that contains the given expressions, has no variables and has specific result type.</summary>
         <returns>The created <see cref="T:System.Linq.Expressions.BlockExpression" />.</returns>
-        <remarks>To be added.</remarks>
+        <remarks>
+          <format type="text/markdown"><![CDATA[
+
+## Remarks
+If you pass a <xref:System.Collections.ObjectModel.ReadOnlyCollection%601> instance as the `expressions` argument, the returned <xref:System.Linq.Expressions.BlockExpression> might reuse that collection instead of copying it. Do not modify the collection's underlying storage after creating the block. If the source can be mutated, create a stable snapshot before passing it to this method.
+
+ ]]></format>
+        </remarks>
       </Docs>
     </Member>
     <Member MemberName="Block">
@@ -2809,7 +2820,14 @@ If the implementing method is `null`:
         <param name="expressions">The expressions in the block.</param>
         <summary>Creates a <see cref="T:System.Linq.Expressions.BlockExpression" /> that contains the given variables and expressions.</summary>
         <returns>The created <see cref="T:System.Linq.Expressions.BlockExpression" />.</returns>
-        <remarks>To be added.</remarks>
+        <remarks>
+          <format type="text/markdown"><![CDATA[
+
+## Remarks
+If you pass a <xref:System.Collections.ObjectModel.ReadOnlyCollection%601> instance as the `expressions` argument, the returned <xref:System.Linq.Expressions.BlockExpression> might reuse that collection instead of copying it. Do not modify the collection's underlying storage after creating the block. If the source can be mutated, create a stable snapshot before passing it to this method.
+
+ ]]></format>
+        </remarks>
       </Docs>
     </Member>
     <Member MemberName="Block">