Machsom means a muzzle or restraint placed on the mouth — both literally for animals and metaphorically for human speech. The word appears in the Psalms in the context of self-restraint: the psalmist resolves to put a muzzle on his own mouth, to guard his tongue from sinful speech, especially when the wicked are watching.
Psalm 39:1 is one of Scripture's most honest struggles: 'I will watch my ways and keep my tongue from sin; I will put a muzzle [machsom] on my mouth while in the presence of the wicked.' This is not permanent silence but disciplined restraint. The theology here connects to James 3 on taming the tongue: unbridled speech causes immense damage, but bridled speech reflects wisdom. The muzzle is an image of costly self-control — the strong choosing to hold back their power. God's own 'silence' in the face of human evil is the ultimate example of restrained speech.