‘This place’ means back to Psalm 95 – ‘If they shall enter into my rest.’ So it’s Genesis in verse 4, and Psalm 95 in verse 5.
The KJV translation of Hebrews 4:5 is literal but results in this conditional clause; other versions remove this in their effort to align with the Hebrew original and introduce a negative particle, but the word ‘if’ is deliberate. The Israelites in the time of Moses had certainly not entered into the promised land and that was a matter of past fact, but the words ‘Today if ye will hear’ (Psalm 95:7) refer to a further opportunity to enter God’s rest, which is made conditional on faith and which governs the interpretation of the words quoted here from the psalm. By trying to align too closely with the original rendering of the words from the Pentateuch (Numbers 14:23), other translations fail to see what the writer to Hebrews is doing in moving now to the yet outstanding offer of rest made by God in the psalm.