Leviticus 2:13
And every oblation of thy meat offering shalt thou season with salt; neither shalt thou suffer the salt of the covenant of thy God to be lacking from thy meat offering: with all thine offerings thou shalt offer salt. And every oblation of thy meat offering shalt thou season with salt; neither shalt thou suffer the salt of the covenant of thy God to be lacking from thy meat offering: with all thine offerings thou shalt offer salt.
The "meat offering" was a food offering made of flour and oil, where "meat" means food in general and not animal flesh. Every offering had to be seasoned with salt, and salt was added to every sacrifice, for an offering lacking salt was unacceptable to God.
Offerings also had to be presented with the sacred fire God commanded, so that salt and this God-kindled fire were both the required divine provision for worship. That sacred fire represents the communication between God and humanity opened through Jesus Christ alone. The incense kindled with that fire represents Christ's mediation mingled with the prayers of God's people.
The salt signifies that only Christ's righteousness can make an offering acceptable to God. Those who present themselves to God must receive that righteousness. Received, it enables them to restrain evil and to exert a saving influence.