Here we see a tendency to replace “these sayings” with “these things”. The first instance occurred when Oliver Cowdery initially wrote down the text in 𝓟. Somewhat later he caught his error, perhaps when he proofed 𝓟 against 𝓞 (the level of ink flow for the supralinear sayings is slightly heavier). The 1830 edition, also a firsthand copy of 𝓞, reads sayings, thus supporting the corrected reading in 𝓟. Oliver Cowdery tended to mix up things and sayings. For another instance where he initially wrote things instead of sayings, see under Mosiah 13:25. For an instance where the opposite error occurred initially in 𝓟, see under Mosiah 6:3. In each case, the critical text will follow the earliest extant reading, thus “these sayings” here in 3 Nephi 16:4.
The second instance of this error in 3 Nephi 16:4 occurred when the compositor for the 1858 Wright edition set the type. In that instance, the subsequent 1874 RLDS edition followed the reading of the 1840 edition, sayings; thus the RLDS text has maintained the correct reading.
Summary: Retain sayings in 3 Nephi 16:4, the 1830 reading as well as the corrected reading in 𝓟.